Ransomware Spotlight: Trigona

28 de listopada de 2023
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Trigona

By Trend Research

After the shutdown of its leak site in October, we look at how ransomware group Trigona operated during its period of activity and discuss how enterprises can fortify their defenses against similar threats.

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The Trigona ransomware, first tracked by Trend Micro as Water Ungaw, emerged in October 2022. However, binaries of the ransomware were first seen as early as June of the same year. While it was active, the group positioned itself as running a lucrative scheme, launching global attacks and advertising revenues up to 20% to 50% for each successful attack. The group was also reported as communicating with network access brokers who provide compromised credentials via the Russian Anonymous Marketplace (RAMP) forum’s internal chats and using the sourced information to obtain initial access to targets.

Threat actors behind the group are known to be affiliated with CryLock due to their similarities in tactics, techniques, and procedures (TTPs), ransom note file name, and email addresses used. In April 2023, Trigona started targeting compromised Microsoft SQL (MSSQL) Servers via brute-force attacks. A month later, we found a Linux version of Trigona that shared similarities with its Windows counterpart.

What organizations need to know about Trigona ransomware

The Trigona ransomware is also linked to BlackCat (also known as AlphaVM, AlphaV, or ALPHV); however, there are currently no known similarities between the two groups. It is possible that BlackCat only utilized or collaborated with the threat actors deploying Trigona.

A report by Arete confirmed that Trigona had been observed exploiting CVE-2021-40539 for initial access. Once it takes hold of a victim’s system and data, threat actors behind Trigona then provide an authorization key for victims to register to the negotiation portal.

Trigona published critical data stolen from victims such as documents and contracts on their leak site. The website featured bidding options to acquire access to the leaked data and contained a countdown timer, which could have served to place more pressure on victims to pay up.

While the pro-Ukraine hacktivist group Ukrainian Cyber Alliance stated that it has taken down Trigona’s leak site in October 2023, ransomware groups often eventually re-emerge under different names while using similar TTPs. This report investigates how the Trigona ransomware group operated during its period of activity to provide information and insights on the ransomware landscape, as well as to serve as reference when the group eventually resurfaces.

Top affected countries and industries according to Trend data

This section cites Trend Micro™ Smart Protection Network™ (SPN) data on Trigona’s attempts to compromise organizations. Note that these detections pertain only to Trend customers and cover only a part of the Trigona victims.

We first detected Trigona attack attempts on Trend customers in July 2023 and noted that the number of attempts peaked the following month. Attempted attacks then declined until the reported shutdown of the ransomware group’s leak site.

Figure 1. A monthly breakdown of Trigona attack attempts in terms of infected machines in 2023 (October 2022 – October 2023)

Figure 1. A monthly breakdown of Trigona attack attempts in terms of infected machines in 2023 (October 2022 – October 2023)
Source: Trend Micro™ Smart Protection Network™


Turkey and the Philippines topped the Trigona attack detections at 23.5% and 19.6%, respectively, while Brazil followed closely at 13.7%. Germany and Thailand rounded up the top five countries targeted by Trigona during its time of activity.

Figure 2. The top six countries with the highest number of attack attempts in terms of infected machines for the Trigona ransomware (October 2022 – October 2023)

Figure 2. The top six countries with the highest number of attack attempts in terms of infected machines for the Trigona ransomware (October 2022 – October 2023)
Source: Trend Micro Smart Protection Network


Industry data showed that threat actors behind Trigona targeted government organizations the most, with attack attempts making up 21.4% of total detections, according to feedback from Trend customers who detailed the industries in which they belong. Trigona also targeted enterprises in the technology, retail, fast-moving consumer goods, and banking industries.

Figure 3. An industry breakdown of Trigona ransomware attack attempts in terms of infected machines (October 2022 – October 2023)

Figure 3. An industry breakdown of Trigona ransomware attack attempts in terms of infected machines (October 2022 – October 2023)
Source: Trend Micro Smart Protection Network

Targeted regions and industries
according to Trigona ransomware’s leak site

This section looks at data based on attacks recorded on the leak site of the Trigona ransomware from April 2023 to October of the same year, when the leak site was taken down. The following data represents organizations that were successfully infiltrated by the Trigona ransomware and which refused to pay the ransom.

Based on a combination of Trend’s open-source intelligence (OSINT) research and investigation of the leak site, Trigona ransomware compromised a total of 33 organizations within the aforementioned period. Of these, 45.5% were organizations operating from North America, while 27.3% were from Europe. Enterprises in Asia-Pacific and Latin America and the Caribbean were also compromised.

Figure 4. The distribution by region of Trigona’s victim organizations

Figure 4. The distribution by region of Trigona’s victim organizations
Sources: Trigona ransomware’s leak site and Trend Micro’s OSINT research
(April 2023 – October 2023)

Based on the leak site data, out of the 13 countries targeted, the United States made up almost half of the victim organizations. Organizations from the United Kingdom made up 9.1%, while Australian organizations made up 6.1% of Trigona’s victims.

Figure 5. The top five countries targeted by the Trigona ransomware

Figure 5. The top five countries targeted by the Trigona ransomware
Sources: Trigona ransomware’s leak site and Trend Micro’s OSINT research
(April 2023 – October 2023)


Threat actors behind the Trigona ransomware targeted enterprises in the finance industry the most, with 18.2% of its victim organizations classified under this trade.

Figure 6. The top five industries targeted by the Trigona ransomware

Figure 6. The top five industries targeted by the Trigona ransomware
Sources: Trigona ransomware’s leak site and Trend Micro’s OSINT research
(April 2023 – October 2023)

Trigona set its sights on small- and medium-sized businesses, which made up more than half of the group’s total victims from April to October 2023.

Figure 7. The distribution by organization size of the Trigona ransomware’s victims

Figure 7. The distribution by organization size of the Trigona ransomware’s victims
Sources: Trigona ransomware’s leak site and Trend Micro’s OSINT research
(April 2023 – October 2023)

Infection chain and techniques

Figure 8. Trigona ransomware’s infection chain

Figure 8. Trigona ransomware’s infection chain

Figure 9. Trigona ransomware’s infection chain when it exploits compromised MSSQL servers

Figure 9. Trigona ransomware’s infection chain when it exploits compromised MSSQL servers


Initial Access

  • Trigona threat actors were observed leveraging the vulnerability CVE-2021-40539.
  • Trigona also targets compromised accounts by obtaining access from network access brokers.

Defense Evasion, Discovery

  • Trigona drops turnoff.bat (detected as Trojan.BAT.TASKILL.AE) and defoff.bat (detected as Trojan.BAT.KILLAV.WLDP and Trojan.BAT.KILLAV.WLDX), which are used to terminate antivirus-related services and processes, including Trend-related service TMBMSRV.exe.
  • Trigona also uses Network Scanner and Advanced Port Scanner to identify network connections. 

Credential Access/Collection

  • Trigona operators use Mimikatz to dump passwords and credentials on victim machines. 

Lateral Movement

  • Trigona operators use Splashtop, a legitimate remote access tool, to drop additional tools in a compromised machine.
  • The threat actors also use other tools, such as LogMeIn, ScreenConnect, AnyDesk, and TeamViewer, for remote access.
  • One of the samples we investigated showed that Trigona could utilize Cobalt Strike to drop MHYPROTINST (detected as Trojan.Win64.MHYPROTINST.A or Trojan.Win64.MHYPROTINST.B), which is used to terminate antivirus processes.

Privilege Escalation

  • Trigona operators make use of Common Language Runtime (CLR) shell on attacks seen on MSSQL servers. The CLR shell tool is capable of multiple commands, one of which drops additional executables for privilege escalation (nt.exe).

Impact

  • The Trigona ransomware encrypts data on victim machines using the Advanced Encryption Standard (AES) algorithm. It contains an encrypted configuration in its resource section that would be decrypted upon execution. However, it will only use certain strings within its configuration during execution. It also randomizes the file names of encrypted files and appends the extension “._locked”.
  • Trigona also uses TDCP_rijndael to encrypt target files. It will only encrypt the first 0x80000 bytes (512 KB) of a file unless executed with the argument /full.

Figure 10. A sample ransom note from the Trigona ransomware group


Additional information

Newer versions of the Trigona ransomware make use of additional command-line arguments. The following table summarizes the command-line arguments it accepts:

/rEncrypts files in random order
/fullEncrypts the whole content of a file; by default, only the first 0x80000 bytes/512 KB are encrypted
/eraseDeletes contents of a file
/!autorunPrevents creating an autorun registry
/is_testingUsed for testing purposes; used with /test_cid and /test_vid
/test_cidUsed to input test CID
/test_vidUsed to input test VID
/pSpecifies path to encrypt
/pathPrevents encrypting local files
/!local
/!lanPrevents encrypting network shares
/shdwnTurns off the machine after encryption
/autorun_onlyInstalls autorun, but does not trigger the encryption

The Linux version of Trigona found in the wild shares similarities with its Windows counterpart. The Linux version of Trigona accepts the following command-line arguments:

/eraseDeletes contents of a file
/is_testingUsed for testing purposes; used with /test_cid and /test_vid
/test_cidUsed to input test CID
/test_vidUsed to input test VID
/pathSpecifies the path to encrypt
/shdwnTurns off the machine after encryption

The 64-bit versions of Trigona found in June 2023 contains the following additional command-line arguments:

/sleepSets the ransomware to “sleep” or be dormant for a specified time before execution
/debugExecutes in debug mode; needs to be executed with /p
/log_fUsed for logging and specifying the log file
/fastMost likely used to speed up encryption, but our analysis showed that this argument doesn’t work
/allow_systemUsed to allow encrypting files in system directory

MITRE tactics and techniques

Initial AccessPersistenceDefense EvasionDiscoveryImpact

T1190 - Exploit Public-Facing Application
Has been observed to exploit the following Zoho ManageEngine ADSelfService Plus authentication bypass vulnerability:

CVE-2021-40539

T1547.001 - Boot or Logon Autostart Execution: Registry Run Keys/Startup Folder
It adds the following registries for automatic execution upon startup:

• HKEY_CURRENT_USER\
Software\Microsoft\Windows\CurrentVersion\Run
• {Generated ID 1} = {Malware File Path}\{Malware name}.exe
• HKEY_CURRENT_USER\
Software\Microsoft\Windows\CurrentVersion\Run
• {Generated ID 2} = %User Temp%\how_to_decrypt.hta

T1140 - Deobfuscate/Decode Files or Information
The Trigona ransomware sample we investigated decrypts its configuration at the resource section named “cfgs.”

T1218.005 - System Binary Proxy Execution: Mshta
Trigona executes the following command to display the ransom note after encryption:

• %System%\mshta.exe %User Temp%\how_to_decrypt.hta

T1036.005 - Masquerading: Match Legitimate Name or Location
Trigona named some samples as svchost.exe to evade detection.

T1497.003 - Virtualization/Sandbox Evasion: Time-Based Evasion
When executed with the argument /sleep {seconds}, the ransomware can “sleep” or be dormant for a period set by the attacker before executing the ransomware.

T1083 - File and Directory Discovery
Trigona enumerates files in the following drives for encryption:

• Fixed drives
• Removable drives
• Network shares

The ransomware also has a specific list of extensions and folders that it can use to verify which files to avoid encrypting.

T1135 - Network Share Discovery
Trigona uses NetShareEnum to look for network shares and encrypt files within network drives.

T1033 - System Owner/User Discovery
• Trigona obtains the following information:
• Computer name
• System time
• OS version
• Drive information
• Disk data
• Keyboard locale

T1529 - System Shutdown/Reboot
Trigona can turn off the infected machine when executed with the command line /shdwn.

T1486 - Data Encrypted for Impact
Trigona uses TDCP_rijndael to encrypt target files. From its configuration, it will choose which files to avoid encrypting. It avoids encrypting files with the following strings in its file path:

• Windows
• System32
• NETFAST

In the sample we investigated, it avoided encrypting files with the following extensions:

• .exe
• .dll
• .sys

Trigona also avoids files with the following characteristics:

• FILE_ATTRIBUTE_
SYSTEM

It also avoids files with the following file names:

• how_to_decrypt.txt

Trigona then drops the following files as its ransom note:

• %User Temp%\how_to_decrypt.hta
• {Encrypted directory}\ how_to_decrypt.hta

It then renames the encrypted files to the following upon encryption:

• available_for_trial.{random}._locked
• {random}._locked

Trigona will only encrypt the first 0x80000 bytes of a file unless executed with the command line /full.

T1485 - Data Destruction
Trigona can delete the first 0x80000 bytes of a file when executed with the command line /erase.

Summary of malware, tools, and exploits used

Initial AccessDefense EvasionDiscoveryLateral MovementPrivilege EscalationImpact
  • CVE-2021-40539
  • turnoff.bat
  • Mimikatz
  • Splashtop
  • CLR shell
  • RDP
  • defoff.bat
  • Cobalt Strike
    • Network Scanner
    • LogMeIn
      • Advanced Port Scanner
      • ScreenConnect
            • AnyDesk
                    • TeamViewer

                      Security recommendations

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                      Despite reports that the Trigona ransomware’s leak site has been shut down, it is worth examining how threat actors behind the group conducted their operations. While relatively new, Trigona successfully facilitated various techniques and created versions to target specific operating systems within its one year of activity. The group, which gained a reputation for imposing intimidating time constraints within which victims were pressured to pay ransom, was also observed targeting data beyond the infected machine and into shared network drives. These behaviors suggest that the threat actors behind the group are quick to adapt, not to mention fierce in carrying out their schemes. Combined with Trigona’s assumed affiliation with CryLock and BlackCat, there is a possibility of the threat actors regrouping after the shutdown and respawning under a different name.

                      To protect systems against ransomware and other similar threats, organizations can implement security frameworks that allocate resources systematically to establish a strong defense strategy.

                      The following are some best practices that organizations can consider to help protect themselves from ransomware infections:


                      Audit and inventory

                      • Take an inventory of assets and data.
                      • Identify authorized and unauthorized devices and software.
                      • Make an audit of event and incident logs.

                      Configure and monitor

                      • Manage hardware and software configurations.
                      • Grant admin privileges and access only when necessary to an employee’s role.
                      • Monitor network ports, protocols, and services.
                      • Activate security configurations on network infrastructure devices such as firewalls and routers.
                      • Establish a software allowlist that executes only legitimate applications.

                      Patch and update

                      • Conduct regular vulnerability assessments.
                      • Perform patching or virtual patching for operating systems and applications.
                      • Update software and applications to their latest versions.

                      Protect and recover

                      • Implement data protection, backup, and recovery measures.
                      • Enable multifactor authentication (MFA).

                      Secure and defend

                      • Employ sandbox analysis to block malicious emails.
                      • Deploy the latest versions of security solutions to all layers of the system, including email, endpoint, web, and network.
                      • Detect early signs of an attack such as the presence of suspicious tools in the system.
                      • Use advanced detection technologies such as those powered by artificial intelligence (AI) and machine learning.

                      Train and test

                      • Regularly train and assess employees in security skills.
                      • Conduct red-team exercises and penetration tests.

                      A multilayered approach can help organizations guard possible entry points into the system (endpoint, email, web, and network). Security solutions that can detect malicious components and suspicious behavior can also help protect enterprises.

                      • Trend Micro Vision One™ provides multilayered protection and behavior detection, which helps block questionable behavior and tools early on before the ransomware can do irreversible damage to the system.
                      • Trend Micro Cloud One™ Workload Security protects systems against both known and unknown threats that exploit vulnerabilities. This protection is made possible through techniques such as virtual patching and machine learning.
                      • Trend Micro™ Deep Discovery™ Email Inspector employs custom sandboxing and advanced analysis techniques to effectively block malicious emails, including phishing emails that can serve as entry points for ransomware.
                      • Trend Micro Apex One™ offers next-level automated threat detection and response against advanced concerns such as fileless threats and ransomware, ensuring the protection of endpoints.

                      Indicators of compromise (IOCs)

                      The IOCs for the threat discussed in this article can be found here. Actual indicators might vary per attack.

                      Trend Micro Vision One Hunting Query

                      Trend Vision One customers can use the following hunting query to check if their network/system is possibly affected by Trigona ransomware:

                      fullPath:"*._locked" OR fullPath:"*available_for_trial*._locked" OR fullPath:"*\\how_to_decrypt.txt" OR malName:"*TRIGONA.*.note" OR malName:"*CRYLOCK.*.note" OR (processFilePath:"*\\mshta.exe" AND filefullpath:"*\\how_to_decrypt.hta") OR (objectRegistryKeyHandle:"*\\Run\\*" AND objectRegistryData:"*\\how_to_decrypt.hta")
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