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17 Mar 2021

AA21-076A: TrickBot Malware

Original release date: March 17, 2021

Summary

This Advisory uses the MITRE Adversarial Tactics, Techniques, and Common Knowledge (ATT&CK®) framework. See the ATT&CK for Enterprise for all referenced threat actor tactics and techniques.

The Cybersecurity and Infrastructure Security Agency (CISA) and Federal Bureau of Investigation (FBI) have observed continued targeting through spearphishing campaigns using TrickBot malware in North America. A sophisticated group of cybercrime actors is luring victims, via phishing emails, with a traffic infringement phishing scheme to download TrickBot.

TrickBot—first identified in 2016—is a Trojan developed and operated by a sophisticated group of cybercrime actors. Originally designed as a banking Trojan to steal financial data, TrickBot has evolved into highly modular, multi-stage malware that provides its operators a full suite of tools to conduct a myriad of illegal cyber activities.

To secure against TrickBot, CISA and FBI recommend implementing the mitigation measures described in this Joint Cybersecurity Advisory, which include blocking suspicious Internet Protocol addresses, using antivirus software, and providing social engineering and phishing training to employees.

Click here for a PDF version of this report.

Technical Details

TrickBot is an advanced Trojan that malicious actors spread primarily by spearphishing campaigns using tailored emails that contain malicious attachments or links, which—if enabled—execute malware (Phishing: Spearphishing Attachment [T1566.001], Phishing: Spearphishing Link [T1566.002]). CISA and FBI are aware of recent attacks that use phishing emails, claiming to contain proof of a traffic violation, to steal sensitive information. The phishing emails contain links that redirect to a website hosted on a compromised server that prompts the victim to click on photo proof of their traffic violation. In clicking the photo, the victim unknowingly downloads a malicious JavaScript file that, when opened, automatically communicates with the malicious actor’s command and control (C2) server to download TrickBot to the victim’s system.

Attackers can use TrickBot to:

  • Drop other malware, such as Ryuk and Conti ransomware, or
  • Serve as an Emotet downloader.[1]

TrickBot uses person-in-the-browser attacks to steal information, such as login credentials (Man in the Browser [T1185]). Additionally, some of TrickBot’s modules spread the malware laterally across a network by abusing the Server Message Block (SMB) Protocol. TrickBot operators have a toolset capable of spanning the entirety of the MITRE ATT&CK framework, from actively or passively gathering information that can be used to support targeting (Reconnaissance [TA0043]), to trying to manipulate, interrupt, or destroy systems and data (Impact [TA0040]).

TrickBot is capable of data exfiltration, cryptomining, and host enumeration (e.g., reconnaissance of Unified Extensible Firmware Interface or Basic Input/Output System [UEFI/BIOS] firmware).[2] For host enumeration, operators deliver TrickBot in modules containing a configuration file with specific tasks.

Figure 1 lays out TrickBot’s use of enterprise techniques.

Figure 1: MITRE ATT&CK enterprise techniques used by TrickBot

 

MITRE ATT&CK Techniques

According to MITRE, TrickBot [S0266] uses the ATT&CK techniques listed in table 1.

Table 1: TrickBot ATT&CK techniques for enterprise

Initial Access [TA0001]

Technique Title

ID Use
Phishing: Spearphishing Attachment T1566.001 TrickBot has used an email with an Excel sheet containing a malicious macro to deploy the malware.
Phishing: Spearphishing Link T1566.002

TrickBot has been delivered via malicious links in phishing emails.

Execution [TA0002]

Technique Title ID Use
Scheduled Task/Job: Scheduled Task T1053.005 TrickBot creates a scheduled task on the system that provides persistence.
Command and Scripting Interpreter: Windows Command Shell T1059.003 TrickBot has used macros in Excel documents to download and deploy the malware on the user’s machine.
Native API T1106 TrickBot uses the Windows Application Programming Interface (API) call, CreateProcessW(), to manage execution flow.
User Execution: Malicious Link T1204.001 TrickBot has sent spearphishing emails in an attempt to lure users to click on a malicious link.
User Execution: Malicious File T1204.002 TrickBot has attempted to get users to launch malicious documents to deliver its payload.

Persistence [TA0003]

Technique Title ID Use
Scheduled Task/Job: Scheduled Task T1053.005 TrickBot creates a scheduled task on the system that provides persistence.
Create or Modify System Process: Windows Service T1543.003 TrickBot establishes persistence by creating an autostart service that allows it to run whenever the machine boots.

Privilege Escalation [TA0004]

Technique Title ID Use
Scheduled Task/Job: Scheduled Task T1053.005 TrickBot creates a scheduled task on the system that provides persistence.
Process Injection: Process Hollowing T1055.012 TrickBot injects into the svchost.exe process.
Create or Modify System Process: Windows Service T1543.003 TrickBot establishes persistence by creating an autostart service that allows it to run whenever the machine boots.

 Defense Evasion [TA0005]

Technique Title ID Use
Obfuscated Files or Information T1027 TrickBot uses non-descriptive names to hide functionality and uses an AES CBC (256 bits) encryption algorithm for its loader and configuration files.
Obfuscated Files or Information: Software Packing T1027.002 TrickBot leverages a custom packer to obfuscate its functionality.
Masquerading T1036 The TrickBot downloader has used an icon to appear as a Microsoft Word document.
Process Injection: Process Hollowing T1055.012 TrickBot injects into the svchost.exe process.
Modify Registry T1112 TrickBot can modify registry entries.
Deobfuscate/Decode Files or Information T1140 TrickBot decodes the configuration data and modules.
Subvert Trust Controls: Code Signing T1553.002 TrickBot has come with a signed downloader component.
Impair Defenses: Disable or Modify Tools T1562.001 TrickBot can disable Windows Defender.

Credential Access [TA0006]

Technique Title ID Use
Input Capture: Credential API Hooking T1056.004 TrickBot has the ability to capture Remote Desktop Protocol credentials by capturing the CredEnumerateA API.
Unsecured Credentials: Credentials in Files T1552.001 TrickBot can obtain passwords stored in files from several applications such as Outlook, Filezilla, OpenSSH, OpenVPN and WinSCP. Additionally, it searches for the .vnc.lnk affix to steal VNC credentials.
Unsecured Credentials: Credentials in Registry T1552.002 TrickBot has retrieved PuTTY credentials by querying the SoftwareSimonTathamPuttySessions registry key.
Credentials from Password Stores T1555 TrickBot can steal passwords from the KeePass open-source password manager.
Credentials from Password Stores: Credentials from Web Browsers T1555.003 TrickBot can obtain passwords stored in files from web browsers such as Chrome, Firefox, Internet Explorer, and Microsoft Edge, sometimes using esentutl.

Discovery [TA0007]

Technique Tactic ID Use
System Service Discovery T1007 TrickBot collects a list of install programs and services on the system’s machine.
System Network Configuration Discovery T1016 TrickBot obtains the IP address, location, and other relevant network information from the victim’s machine.
Remote System Discovery T1018 TrickBot can enumerate computers and network devices.
System Owner/User Discovery T1033 TrickBot can identify the user and groups the user belongs to on a compromised host.
Permission Groups Discovery T1069 TrickBot can identify the groups the user on a compromised host belongs to.
System Information Discovery T1082 TrickBot gathers the OS version, machine name, CPU type, amount of RAM available from the victim’s machine.
File and Directory Discovery T1083 TrickBot searches the system for all of the following file extensions: .avi, .mov, .mkv, .mpeg, .mpeg4, .mp4, .mp3, .wav, .ogg, .jpeg, .jpg, .png, .bmp, .gif, .tiff, .ico, .xlsx, and .zip. It can also obtain browsing history, cookies, and plug-in information.
Account Discovery: Local Account T1087.001 TrickBot collects the users of the system.
Account Discovery: Email Account T1087.003 TrickBot collects email addresses from Outlook.
Domain Trust Discovery T1482 TrickBot can gather information about domain trusts by utilizing Nltest.

Collection [TA0009]

Technique Tactic ID Use
Data from Local System T1005 TrickBot collects local files and information from the victim’s local machine.
Input Capture:Credential API Hooking T1056.004 TrickBot has the ability to capture Remote Desktop Protocol credentials by capturing the CredEnumerateA API.
Person in the Browser T1185 TrickBot uses web injects and browser redirection to trick the user into providing their login credentials on a fake or modified webpage.

Command and Control [TA0011]

Technique Tactic ID Use
Fallback Channels T1008 TrickBot can use secondary command and control (C2) servers for communication after establishing connectivity and relaying victim information to primary C2 servers.
Application Layer Protocol: Web Protocols T1071.001 TrickBot uses HTTPS to communicate with its C2 servers, to get malware updates, modules that perform most of the malware logic and various configuration files.
Ingress Tool Transfer T1105 TrickBot downloads several additional files and saves them to the victim’s machine.
Data Encoding: Standard Encoding T1132.001 TrickBot can Base64-encode C2 commands.
Non-Standard Port T1571 Some TrickBot samples have used HTTP over ports 447 and 8082 for C2.
Encrypted Channel: Symmetric Cryptography T1573.001 TrickBot uses a custom crypter leveraging Microsoft’s CryptoAPI to encrypt C2 traffic.

Exfiltration [TA0010]

Technique Tactic ID Use
Exfiltration Over C2 Channel T1041 TrickBot can send information about the compromised host to a hardcoded C2 server.

Detection

Signatures

CISA developed the following snort signature for use in detecting network activity associated with TrickBot activity.

 

alert tcp any [443,447] -> any any (msg:”TRICKBOT:SSL/TLS Server X.509 Cert Field contains ‘example.com’ (Hex)”; sid:1; rev:1; flow:established,from_server; ssl_state:server_hello; content:”|0b|example.com”; fast_pattern:only; content:”Global Security”; content:”IT Department”; pcre:”/(?:x09x00xc0xb9x3bx93x72xa3xf6xd2|x00xe2x08xffxfbx7bx53x76x3d)/”; classtype:bad-unknown; metadata:service ssl,service and-ports;)

 

alert tcp any any -> any $HTTP_PORTS (msg:”TRICKBOT_ANCHOR:HTTP URI GET contains ‘/anchor'”; sid:1; rev:1; flow:established,to_server; content:”/anchor”; http_uri; fast_pattern:only; content:”GET”; nocase; http_method; pcre:”/^/anchor_?.{3}/[w_-]+.[A-F0-9]+/?$/U”; classtype:bad-unknown; priority:1; metadata:service http;)

 

alert tcp any $SSL_PORTS -> any any (msg:”TRICKBOT:SSL/TLS Server X.509 Cert Field contains ‘C=XX, L=Default City, O=Default Company Ltd'”; sid:1; rev:1; flow:established,from_server; ssl_state:server_hello; content:”|31 0b 30 09 06 03 55 04 06 13 02|XX”; nocase; content:”|31 15 30 13 06 03 55 04 07 13 0c|Default City”; nocase; content:”|31 1c 30 1a 06 03 55 04 0a 13 13|Default Company Ltd”; nocase; content:!”|31 0c 30 0a 06 03 55 04 03|”; classtype:bad-unknown; reference:url,www.virustotal.com/gui/file/e9600404ecc42cf86d38deedef94068db39b7a0fd06b3b8fb2d8a3c7002b650e/detection; metadata:service ssl;)

 

alert tcp any any -> any $HTTP_PORTS (msg:”TRICKBOT:HTTP Client Header contains ‘boundary=Arasfjasu7′”; sid:1; rev:1; flow:established,to_server; content:”boundary=Arasfjasu7|0d 0a|”; http_header; content:”name=|22|proclist|22|”; http_header; content:!”Referer”; content:!”Accept”; content:”POST”; http_method; classtype:bad-unknown; metadata:service http;)

 

alert tcp any any -> any $HTTP_PORTS (msg:”TRICKBOT:HTTP Client Header contains ‘User-Agent|3a 20|WinHTTP loader/1.'”; sid:1; rev:1; flow:established,to_server; content:”User-Agent|3a 20|WinHTTP loader/1.”; http_header; fast_pattern:only; content:”.png|20|HTTP/1.”; pcre:”/^Hostx3ax20(?:d{1,3}.){3}d{1,3}(?:x3ad{2,5})?$/mH”; content:!”Accept”; http_header; content:!”Referer|3a 20|”; http_header; classtype:bad-unknown; metadata:service http;)

 

alert tcp any $HTTP_PORTS -> any any (msg:”TRICKBOT:HTTP Server Header contains ‘Server|3a 20|Cowboy'”; sid:1; rev:1; flow:established,from_server; content:”200″; http_stat_code; content:”Server|3a 20|Cowboy|0d 0a|”; http_header; fast_pattern; content:”content-length|3a 20|3|0d 0a|”; http_header; file_data; content:”/1/”; depth:3; isdataat:!1,relative; classtype:bad-unknown; metadata:service http;)

 

alert tcp any any -> any $HTTP_PORTS (msg:”TRICKBOT:HTTP URI POST contains C2 Exfil”; sid:1; rev:1; flow:established,to_server; content:”Content-Type|3a 20|multipart/form-data|3b 20|boundary=——Boundary”; http_header; fast_pattern; content:”User-Agent|3a 20|”; http_header; distance:0; content:”Content-Length|3a 20|”; http_header; distance:0; content:”POST”; http_method; pcre:”/^/[a-z]{3}d{3}/.+?.[A-F0-9]{32}/d{1,3}//U”; pcre:”/^Hostx3ax20(?:d{1,3}.){3}d{1,3}$/mH”; content:!”Referer|3a|”; http_header; classtype:bad-unknown; metadata:service http;)

 

alert tcp any any -> any $HTTP_PORTS (msg:”HTTP URI GET/POST contains ‘/56evcxv’ (Trickbot)”; sid:1; rev:1; flow:established,to_server; content:”/56evcxv”; http_uri; fast_pattern:only; classtype:bad-unknown; metadata:service http;)

 

alert icmp any any -> any any (msg:”TRICKBOT_ICMP_ANCHOR:ICMP traffic conatins ‘hanc'”; sid:1; rev:1; itype:8; content:”hanc”; offset:4; fast_pattern; classtype:bad-unknown;)

 

alert tcp any any -> any $HTTP_PORTS (msg:”HTTP Client Header contains POST with ‘host|3a 20|*.onion.link’ and ‘data=’ (Trickbot/Princess Ransomeware)”; sid:1; rev:1; flow:established,to_server; content:”POST”; nocase; http_method; content:”host|3a 20|”; http_header; content:”.onion.link”; nocase; http_header; distance:0; within:47; fast_pattern; file_data; content:”data=”; distance:0; within:5; classtype:bad-unknown; metadata:service http;)

 

alert tcp any any -> any $HTTP_PORTS (msg:”HTTP Client Header contains ‘host|3a 20|tpsci.com’ (trickbot)”; sid:1; rev:1; flow:established,to_server; content:”host|3a 20|tpsci.com”; http_header; fast_pattern:only; classtype:bad-unknown; metadata:service http;)

Mitigations

CISA and FBI recommend that network defenders—in federal, state, local, tribal, territorial governments, and the private sector—consider applying the following best practices to strengthen the security posture of their organization’s systems. System owners and administrators should review any configuration changes prior to implementation to avoid negative impacts.

  • Provide social engineering and phishing training to employees.
  • Consider drafting or updating a policy addressing suspicious emails  that specifies users must report all suspicious emails to the security and/or IT departments.
  • Mark external emails with a banner denoting the email is from an external source to assist users in detecting spoofed emails.
  • Implement Group Policy Object and firewall rules.
  • Implement an antivirus program and a formalized patch management process.
  • Implement filters at the email gateway and block suspicious IP addresses at the firewall.
  • Adhere to the principle of least privilege.
  • Implement a Domain-Based Message Authentication, Reporting & Conformance validation system.
  • Segment and segregate networks and functions.
  • Limit unnecessary lateral communications between network hoses, segments and devices.
  • Consider using application allowlisting technology on all assets to ensure that only authorized software executes, and all unauthorized software is blocked from executing on assets. Ensure that such technology only allows authorized, digitally signed scripts to run on a system.
  • Enforce multi-factor authentication.
  • Enable a firewall on agency workstations configured to deny unsolicited connection requests.
  • Disable unnecessary services on agency workstations and servers.
  • Implement an Intrusion Detection System, if not already used, to detect C2 activity and other potentially malicious network activity
  • Monitor web traffic. Restrict user access to suspicious or risky sites.
  • Maintain situational awareness of the latest threats and implement appropriate access control lists.
  • Disable the use of SMBv1 across the network and require at least SMBv2 to harden systems against network propagation modules used by TrickBot.
  • Visit the MITRE ATT&CK Techniques pages (linked in table 1 above) for additional mitigation and detection strategies.
  • See CISA’s Alert on Technical Approaches to Uncovering and Remediating Malicious Activity for more information on addressing potential incidents and applying best practice incident response procedures.

For additional information on malware incident prevention and handling, see the National Institute of Standards and Technology Special Publication 800-83, Guide to Malware Incident Prevention and Handling for Desktops and Laptops.

Resources

References

Revisions

  • March 17, 2021: Initial Version

This product is provided subject to this Notification and this Privacy & Use policy.

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