Note: This alert does not apply to federally certified voting systems running Windows 7. Microsoft will continue to provide free security updates to those systems through the 2020 election. See Microsoft’s article, Extending free Windows 7 security updates to voting systems, for more information.
On January 14, 2020, Microsoft will end extended support for their Windows 7 and Windows Server 2008 R2 operating systems. After this date, these products will no longer receive free technical support, or software and security updates.
Organizations that have regulatory obligations may find that they are unable to satisfy compliance requirements while running Windows 7 and Windows Server 2008 R2.
All software products have a lifecycle. “End of support” refers to the date when the software vendor will no longer provide automatic fixes, updates, or online technical assistance. 
For more information on end of support for Microsoft products see the Microsoft End of Support FAQ.
Systems running Windows 7 and Windows Server 2008 R2 will continue to work at their current capacity even after support ends on January 14, 2020. However, using unsupported software may increase the likelihood of malware and other security threats. Mission and business functions supported by systems running Windows 7 and Windows Server 2008 R2 could experience negative consequences resulting from unpatched vulnerabilities and software bugs. These negative consequences could include the loss of confidentiality, integrity, and availability of data, system resources, and business assets.
The Cybersecurity and Infrastructure Security Agency (CISA) encourages users and organizations to:
The Cybersecurity and Infrastructure Security Agency (CISA) is issuing this Activity Alert to provide information on a vulnerability, known as “BlueKeep,” that exists in the following Microsoft Windows Operating Systems (OSs), including both 32- and 64-bit versions, as well as all Service Pack versions:
An attacker can exploit this vulnerability to take control of an affected system.
BlueKeep (CVE-2019-0708) exists within the Remote Desktop Protocol (RDP) used by the Microsoft Windows OSs listed above. An attacker can exploit this vulnerability to perform remote code execution on an unprotected system.
According to Microsoft, an attacker can send specially crafted packets to one of these operating systems that has RDP enabled. After successfully sending the packets, the attacker would have the ability to perform a number of actions: adding accounts with full user rights; viewing, changing, or deleting data; or installing programs. This exploit, which requires no user interaction, must occur before authentication to be successful.
BlueKeep is considered “wormable” because malware exploiting this vulnerability on a system could propagate to other vulnerable systems; thus, a BlueKeep exploit would be capable of rapidly spreading in a fashion similar to the WannaCry malware attacks of 2017.
CISA has coordinated with external stakeholders and determined that Windows 2000 is vulnerable to BlueKeep.
CISA encourages users and administrators review the Microsoft Security Advisory  and the Microsoft Customer Guidance for CVE-2019-0708  and apply the appropriate mitigation measures as soon as possible:
For OSs that do not have patches or systems that cannot be patched, other mitigation steps can be used to help protect against BlueKeep:
The Cybersecurity and Infrastructure Security Agency (CISA) is issuing this activity alert in response to recently disclosed exploits that target unsecure configurations of SAP components. 
A presentation at the April 2019 Operation for Community Development and Empowerment (OPCDE) cybersecurity conference describes SAP systems with unsecure configurations exposed to the internet. Typically, SAP systems are not intended to be exposed to the internet as it is an untrusted network. Malicious cyber actors can attack and compromise these unsecure systems with publicly available exploit tools, termed “10KBLAZE.” The presentation details the new exploit tools and reports on systems exposed to the internet.
The SAP Gateway allows non-SAP applications to communicate with SAP applications. If SAP Gateway access control lists (ACLs) are not configured properly (e.g., gw/acl_mode = 0), anonymous users can run operating system (OS) commands. According to the OPCDE presentation, about 900 U.S. internet-facing systems were detected in this vulnerable condition.
The SAP router is a program that helps connect SAP systems with external networks. The default
secinfo configuration for a SAP Gateway allows any internal host to run OS commands anonymously. If an attacker can access a misconfigured SAP router, the router can act as an internal host and proxy the attacker’s requests, which may result in remote code execution.
According to the OPCDE presentation, 1,181 SAP routers were exposed to the internet. It is unclear if the exposed systems were confirmed to be vulnerable or were simply running the SAP router service.
SAP Message Servers act as brokers between Application Servers (AS). By default, Message Servers listen on a port 39XX and have no authentication. If an attacker can access a Message Server, they can redirect and/or execute legitimate man-in-the-middle (MITM) requests, thereby gaining credentials. Those credentials can be used to execute code or operations on AS servers (assuming the attacker can reach them). According to the OPCDE presentation, there are 693 Message Servers exposed to the internet in the United States. The Message Server ACL must be protected by the customer in all releases.
CISA worked with security researchers from Onapsis Inc. to develop the following Snort signature that can be used to detect the exploits:
CISA recommends administrators of SAP systems implement the following to mitigate the vulnerabilities included in the OPCDE presentation:
secinfo) and Message Servers (
rdisp/msserv=0 rdisp/msserv_internal=39NN. 
tcp/39NN) to clients or the internet.
The National Cybersecurity and Communications Integration Center (NCCIC), part of the Cybersecurity and Infrastructure Security Agency (CISA), is aware of a global Domain Name System (DNS) infrastructure hijacking campaign. Using compromised credentials, an attacker can modify the location to which an organization’s domain name resources resolve. This enables the attacker to redirect user traffic to attacker-controlled infrastructure and obtain valid encryption certificates for an organization’s domain names, enabling man-in-the-middle attacks.
See the following links for downloadable copies of open-source indicators of compromise (IOCs) from the sources listed in the References section below:
Note: these files were last updated February 13, 2019, to remove the following three non-malicious IP addresses:
Using the following techniques, attackers have redirected and intercepted web and mail traffic, and could do so for other networked services.
NCCIC recommends the following best practices to help safeguard networks against this threat:
The Department of Homeland Security (DHS) National Cybersecurity and Communications Integration Center (NCCIC) and the Federal Bureau of Investigation (FBI) are issuing this activity alert to inform computer network defenders about SamSam ransomware, also known as MSIL/Samas.A. Specifically, this product shares analysis of vulnerabilities that cyber actors exploited to deploy this ransomware. In addition, this report provides recommendations for prevention and mitigation.
The SamSam actors targeted multiple industries, including some within critical infrastructure. Victims were located predominately in the United States, but also internationally. Network-wide infections against organizations are far more likely to garner large ransom payments than infections of individual systems. Organizations that provide essential functions have a critical need to resume operations quickly and are more likely to pay larger ransoms.
The actors exploit Windows servers to gain persistent access to a victim’s network and infect all reachable hosts. According to reporting from victims in early 2016, cyber actors used the JexBoss Exploit Kit to access vulnerable JBoss applications. Since mid-2016, FBI analysis of victims’ machines indicates that cyber actors use Remote Desktop Protocol (RDP) to gain persistent access to victims’ networks. Typically, actors either use brute force attacks or stolen login credentials. Detecting RDP intrusions can be challenging because the malware enters through an approved access point.
After gaining access to a particular network, the SamSam actors escalate privileges for administrator rights, drop malware onto the server, and run an executable file, all without victims’ action or authorization. While many ransomware campaigns rely on a victim completing an action, such as opening an email or visiting a compromised website, RDP allows cyber actors to infect victims with minimal detection.
Analysis of tools found on victims’ networks indicated that successful cyber actors purchased several of the stolen RDP credentials from known darknet marketplaces. FBI analysis of victims’ access logs revealed that the SamSam actors can infect a network within hours of purchasing the credentials. While remediating infected systems, several victims found suspicious activity on their networks unrelated to SamSam. This activity is a possible indicator that the victims’ credentials were stolen, sold on the darknet, and used for other illegal activity.
SamSam actors leave ransom notes on encrypted computers. These instructions direct victims to establish contact through a Tor hidden service site. After paying the ransom in Bitcoin and establishing contact, victims usually receive links to download cryptographic keys and tools to decrypt their network.
NCCIC recommends organizations review the following SamSam Malware Analysis Reports. The reports represent four SamSam malware variants. This is not an exhaustive list.
For general information on ransomware, see the NCCIC Security Publication at https://www.us-cert.gov/security-publications/Ransomware.
DHS and FBI recommend that users and administrators consider using the following best practices to strengthen the security posture of their organization's systems. System owners and administrators should review any configuration changes before implementation to avoid unwanted impacts.
Additional information on malware incident prevention and handling can be found in Special Publication 800-83, Guide to Malware Incident Prevention and Handling for Desktops and Laptops, from the National Institute of Standards and Technology.
To report an intrusion and request resources for incident response or technical assistance, contact NCCIC, FBI, or the FBI’s Cyber Division via the following information:
DHS strives to make this report a valuable tool for our partners and welcomes feedback on how this publication could be improved. You can help by answering a few short questions about this report at the following URL: https://www.us-cert.gov/forms/feedback.
This joint Technical Alert (TA) is the result of analytic efforts between the Department of Homeland Security (DHS) and the Federal Bureau of Investigation (FBI). DHS and FBI are releasing this TA to provide information about a major online ad fraud operation—referred to by the U.S. Government as "3ve"—involving the control of over 1.7 million unique Internet Protocol (IP) addresses globally, when sampled over a 10-day window.
Online advertisers desire premium websites on which to publish their ads and large numbers of visitors to view those ads. 3ve created fake versions of both (websites and visitors), and funneled the advertising revenue to cyber criminals. 3ve obtained control over 1.7 million unique IPs by leveraging victim computers infected with Boaxxe/Miuref and Kovter malware, as well as Border Gateway Protocol-hijacked IP addresses.
Boaxxe malware is spread through email attachments and drive-by downloads. The ad fraud scheme that utilizes the Boaxxe botnet is primarily located in a data center. Hundreds of machines in this data center are browsing to counterfeit websites. When these counterfeit webpages are loaded into a browser, requests are made for ads to be placed on these pages. The machines in the data center use the Boaxxe botnet as a proxy to make requests for these ads. A command and control (C2) server sends instructions to the infected botnet computers to make the ad requests in an effort to hide their true data center IPs.
Kovter malware is also spread through email attachments and drive-by downloads. The ad fraud scheme that utilizes the Kovter botnet runs a hidden Chromium Embedded Framework (CEF) browser on the infected machine that the user cannot see. A C2 server tells the infected machine to visit counterfeit websites. When the counterfeit webpage is loaded in the hidden browser, requests are made for ads to be placed on these counterfeit pages. The infected machine receives the ads and loads them into the hidden browser.
For the indicators of compromise (IOCs) below, keep in mind that any one indicator on its own may not necessarily mean that a machine is infected. Some IOCs may be present for legitimate applications and network traffic as well, but are included here for completeness.
Boaxxe malware leaves several executables on the infected machine. They may be found in one or more of the following locations:
%UserProfile%\AppData\Local\<Random eight-character folder name>\<original file name>.exe
The HKEY_CURRENT_USER (HKCU) “Run” key is set to the path to one of the executables created above.
HKCU\Software\Microsoft\Windows\CurrentVersion\Run\<Above path to executable>\
Kovter malware is found mostly in the registry, but the following files may be found on the infected machine:
%UserProfile%\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.IE5\<RANDOM>\<RANDOM FILENAME>.exe
Kovter is known to hide in the registry under:
The customized CEF browser is dropped to:
The keys will look like random values and contain scripts. In some values, a User-Agent string can be clearly identified. An additional key containing a link to a batch script on the hard drive may be placed within registry key:
There are several patterns in the network requests that are made by Kovter malware when visiting the counterfeit websites. The following are regex rules for these URL patterns:
The following is a YARA rule for detecting Kovter:
If you believe you may be a victim of 3ve and its associated malware or hijacked IPs, and have information that may be useful to investigators, submit your complaint to www.ic3.gov and use the hashtag 3ve (#3ve) in the body of your complaint.
DHS and FBI advise users to take the following actions to remediate malware infections associated with Boaxxe/Miuref or Kovter:
In it we highlight the use of five publicly available tools, which have been used for malicious purposes in recent cyber incidents around the world. The five tools are:
To aid the work of network defenders and systems administrators, we also provide advice on limiting the effectiveness of these tools and detecting their use on a network.
The individual tools we cover in this report are limited examples of the types of tools used by threat actors. You should not consider this an exhaustive list when planning your network defense.
Tools and techniques for exploiting networks and the data they hold are by no means the preserve of nation states or criminals on the dark web. Today, malicious tools with a variety of functions are widely and freely available for use by everyone from skilled penetration testers, hostile state actors and organized criminals, to amateur cyber criminals.
The tools in this Activity Alert have been used to compromise information across a wide range of critical sectors, including health, finance, government, and defense. Their widespread availability presents a challenge for network defense and threat-actor attribution.
Experience from all our countries makes it clear that, while cyber threat actors continue to develop their capabilities, they still make use of established tools and techniques. Even the most sophisticated threat actor groups use common, publicly available tools to achieve their objectives.
Whatever these objectives may be, initial compromises of victim systems are often established through exploitation of common security weaknesses. Abuse of unpatched software vulnerabilities or poorly configured systems are common ways for a threat actor to gain access. The tools detailed in this Activity Alert come into play once a compromise has been achieved, enabling attackers to further their objectives within the victim’s systems.
The tools detailed in this Activity Alert fall into five categories: Remote Access Trojans (RATs), webshells, credential stealers, lateral movement frameworks, and command and control (C2) obfuscators.
This Activity Alert provides an overview of the threat posed by each tool, along with insight into where and when it has been deployed by threat actors. Measures to aid detection and limit the effectiveness of each tool are also described.
The Activity Alert concludes with general advice for improving network defense practices.
First observed in May 2015, the JBiFrost RAT is a variant of the Adwind RAT, with roots stretching back to the Frutas RAT from 2012.
A RAT is a program that, once installed on a victim’s machine, allows remote administrative control. In a malicious context, it can—among many other functions—be used to install backdoors and key loggers, take screen shots, and exfiltrate data.
Malicious RATs can be difficult to detect because they are normally designed not to appear in lists of running programs and can mimic the behavior of legitimate applications.
To prevent forensic analysis, RATs have been known to disable security measures (e.g., Task Manager) and network analysis tools (e.g., Wireshark) on the victim’s system.
JBiFrost RAT is typically employed by cyber criminals and low-skilled threat actors, but its capabilities could easily be adapted for use by state-sponsored threat actors.
Other RATs are widely used by Advanced Persistent Threat (APT) actor groups, such as Adwind RAT, against the aerospace and defense sector; or Quasar RAT, by APT10, against a broad range of sectors.
Threat actors have repeatedly compromised servers in our countries with the purpose of delivering malicious RATs to victims, either to gain remote access for further exploitation, or to steal valuable information such as banking credentials, intellectual property, or PII.
JBiFrost RAT is Java-based, cross-platform, and multifunctional. It poses a threat to several different operating systems, including Windows, Linux, MAC OS X, and Android.
JBiFrost RAT allows threat actors to pivot and move laterally across a network or install additional malicious software. It is primarily delivered through emails as an attachment, usually an invoice notice, request for quotation, remittance notice, shipment notification, payment notice, or with a link to a file hosting service.
Past infections have exfiltrated intellectual property, banking credentials, and personally identifiable information (PII). Machines infected with JBiFrost RAT can also be used in botnets to carry out distributed denial-of-service attacks.
Since early 2018, we have observed an increase in JBiFrost RAT being used in targeted attacks against critical national infrastructure owners and their supply chain operators. There has also been an increase in the RAT’s hosting on infrastructure located in our countries.
In early 2017, Adwind RAT was deployed via spoofed emails designed to look as if they originated from Society for Worldwide Interbank Financial Telecommunication, or SWIFT, network services.
Many other publicly available RATs, including variations of Gh0st RAT, have also been observed in use against a range of victims worldwide.
Some possible indications of a JBiFrost RAT infection can include, but are not limited to:
Protection is best afforded by ensuring systems and installed applications are all fully patched and updated. The use of a modern antivirus program with automatic definition updates and regular system scans will also help ensure that most of the latest variants are stopped in their tracks. You should ensure that your organization is able to collect antivirus detections centrally across its estate and investigate RAT detections efficiently.
Strict application whitelisting is recommended to prevent infections from occurring.
The initial infection mechanism for RATs, including JBiFrost RAT, can be via phishing emails. You can help prevent JBiFrost RAT infections by stopping these phishing emails from reaching your users, helping users to identify and report phishing emails, and implementing security controls so that the malicious email does not compromise your device. The United Kingdom National Cyber Security Centre (UK NCSC) has published phishing guidance.
China Chopper is a publicly available, well-documented webshell that has been in widespread use since 2012.
Webshells are malicious scripts that are uploaded to a target host after an initial compromise and grant a threat actor remote administrative capability.
Once this access is established, webshells can also be used to pivot to additional hosts within a network.
China Chopper is extensively used by threat actors to remotely access compromised web servers, where it provides file and directory management, along with access to a virtual terminal on the compromised device.
As China Chopper is just 4 KB in size and has an easily modifiable payload, detection and mitigation are difficult for network defenders.
China Chopper has two main components: the China Chopper client-side, which is run by the attacker, and the China Chopper server, which is installed on the victim web server but is also attacker-controlled.
The webshell client can issue terminal commands and manage files on the victim server. Its MD5 hash is publicly available (originally posted on hxxp://www.maicaidao.com).
The MD5 hash of the web client is shown in table 1 below.
Table 1: China Chopper webshell client MD5 hash
|Webshell Client||MD5 Hash|
The webshell server is uploaded in plain text and can easily be changed by the attacker. This makes it harder to define a specific hash that can identify adversary activity. In summer 2018, threat actors were observed targeting public-facing web servers that were vulnerable to CVE-2017-3066. The activity was related to a vulnerability in the web application development platform Adobe ColdFusion, which enabled remote code execution.
China Chopper was intended as the second-stage payload, delivered once servers had been compromised, allowing the threat actor remote access to the victim host. After successful exploitation of a vulnerability on the victim machine, the text-based China Chopper is placed on the victim web server. Once uploaded, the webshell server can be accessed by the threat actor at any time using the client application. Once successfully connected, the threat actor proceeds to manipulate files and data on the web server.
China Chopper’s capabilities include uploading and downloading files to and from the victim using the file-retrieval tool
wget to download files from the internet to the target; and editing, deleting, copying, renaming, and even changing the timestamp, of existing files.
The most powerful defense against a webshell is to avoid the web server being compromised in the first place. Ensure that all the software running on public-facing web servers is up-to-date with security patches applied. Audit custom applications for common web vulnerabilities.
One attribute of China Chopper is that every action generates a hypertext transfer protocol (HTTP) POST. This can be noisy and is easily spotted if investigated by a network defender.
While the China Chopper webshell server upload is plain text, commands issued by the client are Base64 encoded, although this is easily decodable.
The adoption of Transport Layer Security (TLS) by web servers has resulted in web server traffic becoming encrypted, making detection of China Chopper activity using network-based tools more challenging.
The most effective way to detect and mitigate China Chopper is on the host itself—specifically on public-facing web servers. There are simple ways to search for the presence of the web-shell using the command line on both Linux and Windows based operating systems.
To detect webshells more broadly, network defenders should focus on spotting either suspicious process execution on web servers (e.g., Hypertext Preprocessor [PHP] binaries spawning processes) and out-of-pattern outbound network connections from web servers. Typically, web servers make predictable connections to an internal network. Changes in those patterns may indicate the presence of a web shell. You can manage network permissions to prevent web-server processes from writing to directories where PHP can be executed, or from modifying existing files.
We also recommend that you use web access logs as a source of monitoring, such as through traffic analytics. Unexpected pages or changes in traffic patterns can be early indicators.
Developed in 2007, Mimikatz is mainly used by attackers to collect the credentials of other users, who are logged into a targeted Windows machine. It does this by accessing the credentials in memory within a Windows process called Local Security Authority Subsystem Service (LSASS).
These credentials, either in plain text, or in hashed form, can be reused to give access to other machines on a network.
Although it was not originally intended as a hacking tool, in recent years Mimikatz has been used by multiple actors for malicious purposes. Its use in compromises around the world has prompted organizations globally to re-evaluate their network defenses.
Mimikatz is typically used by threat actors once access has been gained to a host and the threat actor wishes to move throughout the internal network. Its use can significantly undermine poorly configured network security.
Mimikatz source code is publicly available, which means anyone can compile their own versions of the new tool and potentially develop new Mimikatz custom plug-ins and additional functionality.
Our cyber authorities have observed widespread use of Mimikatz among threat actors, including organized crime and state-sponsored groups.
Once a threat actor has gained local administrator privileges on a host, Mimikatz provides the ability to obtain the hashes and clear-text credentials of other users, enabling the threat actor to escalate privileges within a domain and perform many other post-exploitation and lateral movement tasks.
For this reason, Mimikatz has been bundled into other penetration testing and exploitation suites, such as PowerShell Empire and Metasploit.
Mimikatz is best known for its ability to retrieve clear text credentials and hashes from memory, but its full suite of capabilities is extensive.
The tool can obtain Local Area Network Manager and NT LAN Manager hashes, certificates, and long-term keys on Windows XP (2003) through Windows 8.1 (2012r2). In addition, it can perform pass-the-hash or pass-the-ticket tasks and build Kerberos “golden tickets.”
Many features of Mimikatz can be automated with scripts, such as PowerShell, allowing a threat actor to rapidly exploit and traverse a compromised network. Furthermore, when operating in memory through the freely available “Invoke-Mimikatz” PowerShell script, Mimikatz activity is very difficult to isolate and identify.
Mimikatz has been used across multiple incidents by a broad range of threat actors for several years. In 2011, it was used by unknown threat actors to obtain administrator credentials from the Dutch certificate authority, DigiNotar. The rapid loss of trust in DigiNotar led to the company filing for bankruptcy within a month of this compromise.
More recently, Mimikatz was used in conjunction with other malicious tools—in the NotPetya and BadRabbit ransomware attacks in 2017 to extract administrator credentials held on thousands of computers. These credentials were used to facilitate lateral movement and enabled the ransomware to propagate throughout networks, encrypting the hard drives of numerous systems where these credentials were valid.
In addition, a Microsoft research team identified use of Mimikatz during a sophisticated cyberattack targeting several high-profile technology and financial organizations. In combination with several other tools and exploited vulnerabilities, Mimikatz was used to dump and likely reuse system hashes.
Updating Windows will help reduce the information available to a threat actor from the Mimikatz tool, as Microsoft seeks to improve the protection offered in each new Windows version.
To prevent Mimikatz credential retrieval, network defenders should disable the storage of clear text passwords in LSASS memory. This is default behavior for Windows 8.1/Server 2012 R2 and later, but can be specified on older systems which have the relevant security patches installed. Windows 10 and Windows Server 2016 systems can be protected by using newer security features, such as Credential Guard.
Credential Guard will be enabled by default if:
You should verify that your physical and virtualized servers meet Microsoft’s minimum requirements for each release of Windows 10 and Windows Server.
Password reuse across accounts, particularly administrator accounts, makes pass-the-hash attacks far simpler. You should set user policies within your organization that discourage password reuse, even across common level accounts on a network. The freely available Local Administrator Password Solution from Microsoft can allow easy management of local administrator passwords, preventing the need to set and store passwords manually.
Network administrators should monitor and respond to unusual or unauthorized account creation or authentication to prevent Kerberos ticket exploitation, or network persistence and lateral movement. For Windows, tools such as Microsoft Advanced Threat Analytics and Azure Advanced Threat Protection can help with this.
Network administrators should ensure that systems are patched and up-to-date. Numerous Mimikatz features are mitigated or significantly restricted by the latest system versions and updates. But no update is a perfect fix, as Mimikatz is continually evolving and new third-party modules are often developed.
Most up-to-date antivirus tools will detect and isolate non-customized Mimikatz use and should therefore be used to detect these instances. But threat actors can sometimes circumvent antivirus systems by running Mimikatz in memory, or by slightly modifying the original code of the tool. Wherever Mimikatz is detected, you should perform a rigorous investigation, as it almost certainly indicates a threat actor is actively present in the network, rather than an automated process at work.
Several of Mimikatz’s features rely on exploitation of administrator accounts. Therefore, you should ensure that administrator accounts are issued on an as-required basis only. Where administrative access is required, you should apply privileged access management principles.
Since Mimikatz can only capture the accounts of those users logged into a compromised machine, privileged users (e.g., domain administrators) should avoid logging into machines with their privileged credentials. Detailed information on securing Active Directory is available from Microsoft.
Network defenders should audit the use of scripts, particularly PowerShell, and inspect logs to identify anomalies. This will aid in identifying Mimikatz or pass-the-hash abuse, as well as in providing some mitigation against attempts to bypass detection software.
PowerShell Empire is an example of a post-exploitation or lateral movement tool. It is designed to allow an attacker (or penetration tester) to move around a network after gaining initial access. Other examples of these tools include Cobalt Strike and Metasploit. PowerShell Empire can also be used to generate malicious documents and executables for social engineering access to networks.
The PowerShell Empire framework was designed as a legitimate penetration testing tool in 2015. PowerShell Empire acts as a framework for continued exploitation once a threat actor has gained access to a system.
The tool provides a threat actor with the ability to escalate privileges, harvest credentials, exfiltrate information, and move laterally across a network. These capabilities make it a powerful exploitation tool. Because it is built on a common legitimate application (PowerShell) and can operate almost entirely in memory, PowerShell Empire can be difficult to detect on a network using traditional antivirus tools.
PowerShell Empire has become increasingly popular among hostile state actors and organized criminals. In recent years we have seen it used in cyber incidents globally across a wide range of sectors.
Initial exploitation methods vary between compromises, and threat actors can configure the PowerShell Empire uniquely for each scenario and target. This, in combination with the wide range of skill and intent within the PowerShell Empire user community, means that the ease of detection will vary. Nonetheless, having a greater understanding and awareness of this tool is a step forward in defending against its use by threat actors.
PowerShell Empire enables a threat actor to carry out a range of actions on a victim’s machine and implements the ability to run PowerShell scripts without needing powershell.exe to be present on the system Its communications are encrypted and its architecture is flexible.
PowerShell Empire uses "modules" to perform more specific malicious actions. These modules provide the threat actor with a customizable range of options to pursue their goals on the victim’s systems. These goals include escalation of privileges, credential harvesting, host enumeration, keylogging, and the ability to move laterally across a network.
PowerShell Empire’s ease of use, flexible configuration, and ability to evade detection make it a popular choice for threat actors of varying abilities.
During an incident in February 2018, a UK energy sector company was compromised by an unknown threat actor. This compromise was detected through PowerShell Empire beaconing activity using the tool’s default profile settings. Weak credentials on one of the victim’s administrator accounts are believed to have provided the threat actor with initial access to the network.
In early 2018, an unknown threat actor used Winter Olympics-themed socially engineered emails and malicious attachments in a spear-phishing campaign targeting several South Korean organizations. This attack had an additional layer of sophistication, making use of
Invoke-PSImage, a stenographic tool that will encode any PowerShell script into an image.
In December 2017, APT19 targeted a multinational law firm with a phishing campaign. APT19 used obfuscated PowerShell macros embedded within Microsoft Word documents generated by PowerShell Empire.
Our cybersecurity authorities are also aware of PowerShell Empire being used to target academia. In one reported instance, a threat actor attempted to use PowerShell Empire to gain persistence using a Windows Management Instrumentation event consumer. However, in this instance, the PowerShell Empire agent was unsuccessful in establishing network connections due to the HTTP connections being blocked by a local security appliance.
Identifying malicious PowerShell activity can be difficult due to the prevalence of legitimate PowerShell activity on hosts and the increased use of PowerShell in maintaining a corporate environment.
To identify potentially malicious scripts, PowerShell activity should be comprehensively logged. This should include script block logging and PowerShell transcripts.
Older versions of PowerShell should be removed from environments to ensure that they cannot be used to circumvent additional logging and controls added in more recent versions of PowerShell. This page provides a good summary of PowerShell security practices.
The code integrity features in recent versions of Windows can be used to limit the functionality of PowerShell, preventing or hampering malicious PowerShell in the event of a successful intrusion.
A combination of script code signing, application whitelisting, and constrained language mode will prevent or limit the effect of malicious PowerShell in the event of a successful intrusion. These controls will also impact legitimate PowerShell scripts and it is strongly advised that they be thoroughly tested before deployment.
When organizations profile their PowerShell usage, they often find it is only used legitimately by a small number of technical staff. Establishing the extent of this legitimate activity will make it easier to monitor and investigate suspicious or unexpected PowerShell usage elsewhere on the network.
Attackers will often want to disguise their location when compromising a target. To do this, they may use generic privacy tools (e.g., Tor) or more specific tools to obfuscate their location.
HUC Packet Transmitter (HTran) is a proxy tool used to intercept and redirect Transmission Control Protocol (TCP) connections from the local host to a remote host. This makes it possible to obfuscate an attacker’s communications with victim networks. The tool has been freely available on the internet since at least 2009.
HTran facilitates TCP connections between the victim and a hop point controlled by a threat actor. Malicious threat actors can use this technique to redirect their packets through multiple compromised hosts running HTran to gain greater access to hosts in a network.
The use of HTran has been regularly observed in compromises of both government and industry targets.
A broad range of threat actors have been observed using HTran and other connection proxy tools to
HTran can run in several modes, each of which forwards traffic across a network by bridging two TCP sockets. They differ in terms of where the TCP sockets are initiated from, either locally or remotely. The three modes are
HTran can inject itself into running processes and install a rootkit to hide network connections from the host operating system. Using these features also creates Windows registry entries to ensure that HTran maintains persistent access to the victim network.
Recent investigations by our cybersecurity authorities have identified the use of HTran to maintain and obfuscate remote access to targeted environments.
In one incident, the threat actor compromised externally-facing web servers running outdated and vulnerable web applications. This access enabled the upload of webshells, which were then used to deploy other tools, including HTran.
HTran was installed into the ProgramData directory and other deployed tools were used to reconfigure the server to accept Remote Desktop Protocol (RDP) communications.
The threat actor issued a command to start HTran as a client, initiating a connection to a server located on the internet over port 80, which forwards RDP traffic from the local interface.
In this case, HTTP was chosen to blend in with other traffic that was expected to be seen originating from a web server to the internet. Other well-known ports used included:
Attackers need access to a machine to install and run HTran, so network defenders should apply security patches and use good access control to prevent attackers from installing malicious applications.
Network monitoring and firewalls can help prevent and detect unauthorized connections from tools such as HTran.
In some of the samples analyzed, the rootkit component of HTran only hides connection details when the proxy mode is used. When client mode is used, defenders can view details about the TCP connections being made.
HTran also includes a debugging condition that is useful for network defenders. In the event that a destination becomes unavailable, HTran generates an error message using the following format:
sprint(buffer, “[SERVER]connection to %s:%d error\r\n”, host, port2);
This error message is relayed to the connecting client in the clear. Network defenders can monitor for this error message to potentially detect HTran instances active in their environments.
There are several measures that will improve the overall cybersecurity of your organization and help protect it against the types of tools highlighted in this report. Network defenders are advised to seek further information using the links below.
Further information: invest in preventing malware-based attacks across various scenarios. See UK NCSC Guidance: https://www.ncsc.gov.uk/guidance/mitigating-malware.
NCCIC encourages recipients of this report to contribute any additional information that they may have related to this threat. For any questions related to this report, please contact NCCIC at
NCCIC encourages you to report any suspicious activity, including cybersecurity incidents, possible malicious code, software vulnerabilities, and phishing-related scams. Reporting forms can be found on the NCCIC/US-CERT homepage at http://www.us-cert.gov/.
NCCIC strives to make this report a valuable tool for our partners and welcomes feedback on how this publication could be improved. You can help by answering a few short questions about this report at the following URL: https://www.us-cert.gov/forms/feedback.
The National Cybersecurity and Communications Integration Center (NCCIC) is aware of ongoing APT actor activity attempting to infiltrate the networks of global managed service providers (MSPs). Since May 2016, APT actors have used various tactics, techniques, and procedures (TTPs) for the purposes of cyber espionage and intellectual property theft. APT actors have targeted victims in several U.S. critical infrastructure sectors, including Information Technology (IT), Energy, Healthcare and Public Health, Communications, and Critical Manufacturing.
This Technical Alert (TA) provides information and guidance to assist MSP customer network and system administrators with the detection of malicious activity on their networks and systems and the mitigation of associated risks. This TA includes an overview of TTPs used by APT actors in MSP network environments, recommended mitigation techniques, and information on reporting incidents.
MSPs provide remote management of customer IT and end-user systems. The number of organizations using MSPs has grown significantly over recent years because MSPs allow their customers to scale and support their network environments at a lower cost than financing these resources internally. MSPs generally have direct and unfettered access to their customers’ networks, and may store customer data on their own internal infrastructure. By servicing a large number of customers, MSPs can achieve significant economies of scale. However, a compromise in one part of an MSP’s network can spread globally, affecting other customers and introducing risk.
Using an MSP significantly increases an organization’s virtual enterprise infrastructure footprint and its number of privileged accounts, creating a larger attack surface for cyber criminals and nation-state actors. By using compromised legitimate MSP credentials (e.g., administration, domain, user), APT actors can move bidirectionally between an MSP and its customers’ shared networks. Bidirectional movement between networks allows APT actors to easily obfuscate detection measures and maintain a presence on victims’ networks.
Note: NCCIC previously released information related to this activity in Alert TA17-117A: Intrusions Affecting Multiple Victims Across Multiple Sectors published on April 27, 2017, which includes indicators of compromise, signatures, suggested detection methods, and recommended mitigation techniques.
APT actors use a range of “living off the land” techniques to maintain anonymity while conducting their attacks. These techniques include using legitimate credentials and trusted off-the-shelf applications and pre-installed system tools present in MSP customer networks.
Pre-installed system tools, such as command line scripts, are very common and used by system administrators for legitimate processes. Command line scripts are used to discover accounts and remote systems.
PowerSploit is a repository of Microsoft PowerShell and Visual Basic scripts and uses system commands such as
netsh. PowerSploit, originally developed as a legitimate penetration testing tool, is widely misused by APT actors. These scripts often cannot be blocked because they are legitimate tools, so APT actors can use them and remain undetected on victim networks. Although network defenders can generate log files, APT actors’ use of legitimate scripts makes it difficult to identify system anomalies and other malicious activity.
When APT actors use system tools and common cloud services, it can also be difficult for network defenders to detect data exfiltration. APT actors have been observed using Robocopy—a Microsoft command line tool—to transfer exfiltrated and archived data from MSP client networks back through MSP network environments. Additionally, APT actors have been observed using legitimate PuTTY Secure Copy Client functions, allowing them to transfer stolen data securely and directly to third-party systems.
A successful network intrusion can have severe impacts to the affected organization, particularly if the compromise becomes public. Possible impacts include
Organizations should configure system logs to detect incidents and to identify the type and scope of malicious activity. Properly configured logs enable rapid containment and appropriate response.
An organization’s ability to rapidly respond to and recover from an incident begins with the development of an incident response capability. An organization’s response capability should focus on being prepared to handle the most common attack vectors (e.g., spearphishing, malicious web content, credential theft). In general, organizations should prepare by
MSP clients that do not conduct the majority of their own network defense should work with their MSP to determine what they can expect in terms of security. MSP clients should understand the supply chain risk associated with their MSP. Organizations should manage risk equally across their security, legal, and procurement groups. MSP clients should also refer to cloud security guidance from the National Institute of Standards and Technology to learn about MSP terms of service, architecture, security controls, and risks associated with cloud computing and data protection.  
Restricting access to networks and systems is critical to containing an APT actor’s movement. Provided below are key items that organizations should implement and periodically audit to ensure their network environment’s physical and logical architecture limits an APT actor’s visibility and access.
Virtual Private Network Connection Recommendations
Network Architecture Recommendations
Network Service Restriction Recommendations
Compromised account credentials continue to be the number one way threat actors are able to penetrate a network environment. The accounts organizations create for MSPs increase the risk of credential compromise, as MSP accounts typically require elevated access. It is important organizations’ adhere to best practices for password and permission management, as this can severely limit a threat actor’s ability to access and move laterally across a network. Provided below are key items organizations should implement and routinely audit to ensure these risks are mitigated.
Account Configuration Recommendations
Logging Configuration Recommendations
Building a sound architecture supported by strong technical controls is only the first part to protecting a network environment. It is just as critical that organizations continuously monitor their systems, update configurations to reflect changes in their network environment, and maintain relationships with MSPs. Listed below are key operational controls organizations should incorporate for protection from threats.
Operational Control Recommendations
It is important to note that—while the recommendations provided in this TA aim at preventing the initial attack vectors and the spread of any malicious activity—there is no single solution to protecting and defending a network. NCCIC recommends network defenders use a defense-in-depth strategy to increase the odds of successfully identifying an intrusion, stopping malware, and disrupting threat actor activity. The goal is to make it as difficult as possible for an attacker to be successful and to force them to use methods that are easier to detect with higher operational costs.
Contact DHS or your local FBI office immediately. To report an intrusion and request resources for incident response or technical assistance, contact NCCIC at ([email protected] or 888-282-0870), FBI through a local field office, or the FBI’s Cyber Division ([email protected] or 855-292-3937).
This technical alert addresses the exploitation of trusted network relationships and the subsequent illicit use of legitimate credentials by Advanced Persistent Threat (APT) actors. It identifies APT actors' tactics, techniques, and procedures (TTPs) and describes the best practices that could be employed to mitigate each of them. The mitigations for each TTP are arranged according to the National Institute of Standards and Technology (NIST) Cybersecurity Framework core functions of Protect, Detect, Respond, and Recover.
APT actors are using multiple mechanisms to acquire legitimate user credentials to exploit trusted network relationships in order to expand unauthorized access, maintain persistence, and exfiltrate data from targeted organizations. Suggested best practices for administrators to mitigate this threat include auditing credentials, remote-access logs, and controlling privileged access and remote access.
APT actors are conducting malicious activity against organizations that have trusted network relationships with potential targets, such as a parent company, a connected partner, or a contracted managed service provider (MSP). APT actors can use legitimate credentials to expand unauthorized access, maintain persistence, exfiltrate data, and conduct other operations, while appearing to be authorized users. Leveraging legitimate credentials to exploit trusted network relationships also allows APT actors to access other devices and other trusted networks, which affords intrusions a high level of persistence and stealth.
Recommended best practices for mitigating this threat include rigorous credential and privileged-access management, as well as remote-access control, and audits of legitimate remote-access logs. While these measures aim to prevent the initial attack vectors and the spread of malicious activity, there is no single proven threat response.
Using a defense-in-depth strategy is likely to increase the odds of successfully disrupting adversarial objectives long enough to allow network defenders to detect and respond before the successful completion of a threat actor’s objectives.
Any organization that uses an MSP to provide services should monitor the MSP's interactions within their organization’s enterprise networks, such as account use, privileges, and access to confidential or proprietary information. Organizations should also ensure that they have the ability to review their security and monitor their information hosted on MSP networks.
The following table displays the TTPs employed by APT actors and pairs them with mitigations that network defenders can implement.
Respond and Recover:
Execution and Internal Reconnaissance:
Respond and Recover:
Compromising the credentials of legitimate users automatically provides a threat actor access to the network resources available to those users and helps that threat actor move more covertly through the network. Adopting and enforcing a strong-password policy can reduce a threat actor’s ability to compromise legitimate accounts; transitioning to multifactor authentication solutions increases the difficulty even further. Additionally, monitoring user account logins—whether failed or successful—and deploying tools and services to detect illicit use of credentials can help network defenders identify potentially malicious activity.
Threat actors regularly target privileged accounts because they not only grant increased access to high-value assets in the network, but also more easily enable lateral movement, and often provide mechanisms for the actors to hide their activities. Privileged access can be controlled by ensuring that only those users requiring elevated privileges are granted those accesses and, in accordance with the principle of least privilege, by restricting the use of those privileged accounts to instances where elevated privileges are required for specific tasks. It is also important to carefully manage and monitor local-administrator and MSP accounts because they inherently function with elevated privileges and are often ignored after initial configuration.
A key way to control privileged accounts is to segregate and control administrator (admin) privileges. All administrative credentials should be tightly controlled, restricted to a function, or even limited to a specific amount of time. For example, only dedicated workstation administrator accounts should be able to administer workstations. Server accounts, such as general, Structured Query Language, or email admins, should not have administrative access to workstations. The only place domain administrator (DA) or enterprise administrator (EA) credentials should ever be used is on a domain controller. Both EA and DA accounts should be removed from the local-administrators group on all other devices. On UNIX devices, sudo (or root) access should be tightly restricted in the same manner. Employing a multifactor authentication solution for admin accounts adds another layer of security and can significantly reduce the impact of a password compromise because the threat actor needs the other factor—that is, a smartcard or a token—for authentication.
Additionally, administrators should disable unencrypted remote-administrative protocols and services, which are often enabled by default. Protocols required for operations must be authorized, and the most secure version must be implemented. All other protocols must be disabled, particularly unencrypted remote-administrative protocols used to manage network infrastructure devices, such as Telnet, Hypertext Transfer Protocol, File Transfer Protocol, Trivial File Transfer Protocol, and Simple Network Management Protocol versions 1 and 2.
Contact DHS or your local FBI office immediately. To report an intrusion and request resources for incident response or technical assistance, contact NCCIC at ([email protected] or 888-282-0870), FBI through a local field office, or the FBI’s Cyber Division ([email protected] or 855-292-3937).
Retail Payment Systems
This joint Technical Alert (TA) is the result of analytic efforts between the Department of Homeland Security (DHS), the Department of the Treasury (Treasury), and the Federal Bureau of Investigation (FBI). Working with U.S. government partners, DHS, Treasury, and FBI identified malware and other indicators of compromise (IOCs) used by the North Korean government in an Automated Teller Machine (ATM) cash-out scheme—referred to by the U.S. Government as “FASTCash.” The U.S. Government refers to malicious cyber activity by the North Korean government as HIDDEN COBRA. For more information on HIDDEN COBRA activity, visit https://www.us-cert.gov/hiddencobra.
FBI has high confidence that HIDDEN COBRA actors are using the IOCs listed in this report to maintain a presence on victims’ networks to enable network exploitation. DHS, FBI, and Treasury are distributing these IOCs to enable network defense and reduce exposure to North Korean government malicious cyber activity.
This TA also includes suggested response actions to the IOCs provided, recommended mitigation techniques, and information on reporting incidents. If users or administrators detect activity associated with the malware families associated with FASTCash, they should immediately flag it, report it to the DHS National Cybersecurity and Communications Integration Center (NCCIC) or the FBI Cyber Watch (CyWatch), and give it the highest priority for enhanced mitigation.
NCCIC conducted analysis on 10 malware samples related to this activity and produced a Malware Analysis Report (MAR). MAR-10201537, HIDDEN COBRA FASTCash-Related Malware, examines the tactics, techniques, and procedures observed in the malware. Visit the MAR-10201537 page for the report and associated IOCs.
Since at least late 2016, HIDDEN COBRA actors have used FASTCash tactics to target banks in Africa and Asia. At the time of this TA’s publication, the U.S. Government has not confirmed any FASTCash incidents affecting institutions within the United States.
FASTCash schemes remotely compromise payment switch application servers within banks to facilitate fraudulent transactions. The U.S. Government assesses that HIDDEN COBRA actors will continue to use FASTCash tactics to target retail payment systems vulnerable to remote exploitation.
According to a trusted partner’s estimation, HIDDEN COBRA actors have stolen tens of millions of dollars. In one incident in 2017, HIDDEN COBRA actors enabled cash to be simultaneously withdrawn from ATMs located in over 30 different countries. In another incident in 2018, HIDDEN COBRA actors enabled cash to be simultaneously withdrawn from ATMs in 23 different countries.
HIDDEN COBRA actors target the retail payment system infrastructure within banks to enable fraudulent ATM cash withdrawals across national borders. HIDDEN COBRA actors have configured and deployed malware on compromised switch application servers in order to intercept and reply to financial request messages with fraudulent but legitimate-looking affirmative response messages. Although the infection vector is unknown, all of the compromised switch application servers were running unsupported IBM Advanced Interactive eXecutive (AIX) operating system versions beyond the end of their service pack support dates; there is no evidence HIDDEN COBRA actors successfully exploited the AIX operating system in these incidents.
HIDDEN COBRA actors exploited the targeted systems by using their knowledge of International Standards Organization (ISO) 8583—the standard for financial transaction messaging—and other tactics. HIDDEN COBRA actors most likely deployed ISO 8583 libraries on the targeted switch application servers. Malicious threat actors use these libraries to help interpret financial request messages and properly construct fraudulent financial response messages.
Figure 1: Anatomy of a FASTCash scheme
A review of log files showed HIDDEN COBRA actors making typos and actively correcting errors while configuring the targeted server for unauthorized activity. Based on analysis of the affected systems, analysts believe that malware—used by HIDDEN COBRA actors and explained in the Technical Details section below—inspected inbound financial request messages for specific primary account numbers (PANs). The malware generated fraudulent financial response messages only for the request messages that matched the expected PANs. Most accounts used to initiate the transactions had minimal account activity or zero balances.
Analysts believe HIDDEN COBRA actors blocked transaction messages to stop denial messages from leaving the switch and used a
GenerateResponse* function to approve the transactions. These response messages were likely sent for specific PANs matched using
CheckPan()verification (see figure 1 for additional details on
HIDDEN COBRA actors used malicious Windows executable applications, command-line utility applications, and other files in the FASTCash campaign to perform transactions and interact with financial systems, including the switch application server. The initial infection vector used to compromise victim networks is unknown; however, analysts surmise HIDDEN COBRA actors used spear-phishing emails in targeted attacks against bank employees. HIDDEN COBRA actors likely used Windows-based malware to explore a bank’s network to identify the payment switch application server. Although these threat actors used different malware in each known incident, static analysis of malware samples indicates similarities in malware capabilities and functionalities.
HIDDEN COBRA actors likely used legitimate credentials to move laterally through a bank’s network and to illicitly access the switch application server. This pattern suggests compromised systems within a bank’s network were used to access and compromise the targeted payment switch application server.
Upon successful compromise of a bank’s payment switch application server, HIDDEN COBRA actors likely injected malicious code into legitimate processes—using command-line utility applications on the payment switch application server—to enable fraudulent behavior by the system in response to what would otherwise be normal payment switch application server activity. NCCIC collaborated with Symantec cybersecurity researchers to provide additional context on existing analysis . Malware samples analyzed included malicious AIX executable files intended for a proprietary UNIX operating system developed by IBM. The AIX executable files were designed to inject malicious code into a currently running process. Two of the AIX executable files are configured with an export function, which allows malicious applications to perform transactions on financial systems using the ISO 8583 standard. See MAR-10201537 for details on the files used. Figure 1 depicts the pattern of fraudulent behavior.
During analysis of log files associated with known FASTCash incidents, analysts identified the following commonalities:
.so(shared object) commands using the following pattern:
/tmp/.ICE-unix/e <PID> /tmp.ICE-unix/<filename>m.so <argument>
.socommand, which contained a similar, but slightly different, command:
./sun <PID>/tmp/.ICE-unix/engine.so <argument>
Additionally, both commands use either the
inject (mode 0) or
eject (mode 1) argument with the following ISO 8583 libraries:
m.so [with argument “0” or “1”]
m1.so [with argument “0” or “1”]
m2.so [with argument “0” or “1”]
m3.so [with argument “0” or “1”]
NCCIC recommends administrators review bash history logs of all users with root privileges. Administrators can find commands entered by users in the bash history logs; these would indicate the execution of malicious code on the switch application server. Administrators should log and monitor all commands.
The U.S. Government recommends that network administrators review MAR-10201537 for IOCs related to the HIDDEN COBRA FASTCash campaign, identify whether any of the provided IOCs fall within their organization’s network, and—if found—take necessary measures to remove the malware.
A successful network intrusion can have severe impacts, particularly if the compromise becomes public. Possible impacts to the affected organization include
Require Chip and Personal Identification Number Cryptogram Validation
Isolate Payment System Infrastructure
Logically Segregate Operating Environments
Encrypt Data in Transit
Monitor for Anomalous Behavior as Part of Layered Security
Recommendations for Organizations with ATM or Point-of-Sale Devices
NCCIC encourages users and administrators to use the following best practices to strengthen the security posture of their organization’s systems:
For additional information on malware incident prevention and handling, see the National Institute of Standards and Technology (NIST) Special Publication (SP) 800-83: Guide to Malware Incident Prevention and Handling for Desktops and Laptops.
Contact DHS or your local FBI office immediately. To report an intrusion and request resources for incident response or technical assistance, contact NCCIC at ([email protected] or 888-282-0870), FBI through a local field office, or the FBI’s Cyber Division ([email protected] or 855-292-3937).