CERT-UA Warns: Dark Crystal RAT Targets Ukrainian Defense via Malicious Signal Messages
Summary:
CERT-UA has issued a warning regarding a new campaign targeting Ukraine's defense sector, utilizing the Dark Crystal RAT (DCRat). They have recorded numerous cases of these cyberattacks. This activity cluster, identified in June 2024, targets both defense-industrial complex enterprises and military personnel. The infection vector involves malicious archived messages distributed via the Signal messaging app, containing archive files with a decoy PDF and a .NET-based cryptor/loader called DarkTortilla. This cryptor decrypts and executes Dark Crystal RAT (DCRat), a remote control software tool, enabling remote command execution, data theft, and device control. In some instances, malicious actors will use pre-compromised accounts from a person's contact list to send messages with the intention of establishing a false sense of trust. The attacks, attributed to the UAC-0200 threat cluster, leverage compromised Signal accounts to enhance credibility following Signal’s official unwillingness to assist Ukrainian law enforcement with nation-state threats. This campaign highlights the growing threat posed by the use of popular messaging apps as attack vectors, particularly in sensitive sectors.
Security Officer Comments:
The targeting of Ukraine's defense sector via Signal follows a recommendation to Americans by CISA to employ encrypted messaging apps for communications following a wave of telecom attacks across dozens of countries and underscores the evolving tactics of state-sponsored threat actors. The use of compromised Signal accounts to distribute malware demonstrates a sophisticated social engineering approach, exploiting trust to bypass defenses. The inclusion of DarkTortilla, a .NET-based cryptor, highlights the attackers' efforts to evade detection. The ongoing dispute between Ukrainian officials and Signal regarding cooperation and responsiveness to cyber threats adds a layer of complexity to the situation. The statement from Ukraine's National Security and Defense Council that Signal's inaction is aiding Russian intelligence, combined with recent reports of Russian actors exploiting device-linking features on messaging platforms, accentuates a broader trend of leveraging encrypted messaging tools for espionage and other cybercriminal activities. This development emphasizes the critical need for user awareness training specifically tailored to smishing attempts, particularly within critical infrastructure and defense organizations, to mitigate the security risks associated with the proliferation of messaging-based attacks. The reliance of the Ukrainian population on Signal as an alternative to Telegram significantly expands the attack surface of organizations involved with Ukraine.
Suggested Corrections:
IOCs are available here.
Users should always be cautious of individuals or organizations that ask for personal information. Most companies will not ask for sensitive data from their customers. If in doubt, users should verify with the company itself to avoid any potential issues.
Users should always take a close look at the sender’s display name when checking the legitimacy of an email. Most companies use a single domain for their URLs and emails, so a message that originates from a different domain is a red flag.
As a general rule, users should not click links or download files even if they come from seemingly “trustworthy” sources.
Check for mismatched URLs. While an embedded URL might seem perfectly valid, hovering above it might show a different web address. In fact, users should avoid clicking links in emails unless they are certain that it is a legitimate link.
Users should always be on the lookout for any grammatical errors and spelling mistakes. Legitimate companies will often employ proofreaders and editors who ensure that the materials they send out are error-free.
Users should not be frightened or intimidated by messages that have an alarmist tone. They should double check with the company if they are uncertain about the status of their accounts.
Phishing emails are designed to be sent to a large number of people, so they need to be as impersonal as possible. Users should check whether the message contains a generic subject and greeting, as this can be a sign of a phishing attempt.
Although not every end user has access to advanced anti-phishing software, they can still use the built-in protection of their email clients to filter messages. One example is setting the email client to block all images unless approved.
Legitimate companies will never send confirmation emails unless there are specific reasons for doing so. In fact, most companies will avoid sending unsolicited messages unless it’s for company updates, newsletters, or advertising purposes.
Users should always take the context of an email or message into account. For example, most online accounts do away with viewable member numbers, so users should be wary if they receive emails containing a “member number” for services that generally don’t use them.
It is important to take note of unusual information in the text of the message. Any mentions of operating systems and software that are not typically used by consumers can often be indicators of a phishing attempt.
If it seems suspicious, it probably is. Users should always err on the side of caution when it comes to sending out personally identifiable information through messages and emails.
Link(s):
https://thehackernews.com/2025/03/cert-ua-warns-dark-crystal-rat-targets.html
https://cert.gov.ua/article/6282737
CERT-UA has issued a warning regarding a new campaign targeting Ukraine's defense sector, utilizing the Dark Crystal RAT (DCRat). They have recorded numerous cases of these cyberattacks. This activity cluster, identified in June 2024, targets both defense-industrial complex enterprises and military personnel. The infection vector involves malicious archived messages distributed via the Signal messaging app, containing archive files with a decoy PDF and a .NET-based cryptor/loader called DarkTortilla. This cryptor decrypts and executes Dark Crystal RAT (DCRat), a remote control software tool, enabling remote command execution, data theft, and device control. In some instances, malicious actors will use pre-compromised accounts from a person's contact list to send messages with the intention of establishing a false sense of trust. The attacks, attributed to the UAC-0200 threat cluster, leverage compromised Signal accounts to enhance credibility following Signal’s official unwillingness to assist Ukrainian law enforcement with nation-state threats. This campaign highlights the growing threat posed by the use of popular messaging apps as attack vectors, particularly in sensitive sectors.
Security Officer Comments:
The targeting of Ukraine's defense sector via Signal follows a recommendation to Americans by CISA to employ encrypted messaging apps for communications following a wave of telecom attacks across dozens of countries and underscores the evolving tactics of state-sponsored threat actors. The use of compromised Signal accounts to distribute malware demonstrates a sophisticated social engineering approach, exploiting trust to bypass defenses. The inclusion of DarkTortilla, a .NET-based cryptor, highlights the attackers' efforts to evade detection. The ongoing dispute between Ukrainian officials and Signal regarding cooperation and responsiveness to cyber threats adds a layer of complexity to the situation. The statement from Ukraine's National Security and Defense Council that Signal's inaction is aiding Russian intelligence, combined with recent reports of Russian actors exploiting device-linking features on messaging platforms, accentuates a broader trend of leveraging encrypted messaging tools for espionage and other cybercriminal activities. This development emphasizes the critical need for user awareness training specifically tailored to smishing attempts, particularly within critical infrastructure and defense organizations, to mitigate the security risks associated with the proliferation of messaging-based attacks. The reliance of the Ukrainian population on Signal as an alternative to Telegram significantly expands the attack surface of organizations involved with Ukraine.
Suggested Corrections:
IOCs are available here.
Users should always be cautious of individuals or organizations that ask for personal information. Most companies will not ask for sensitive data from their customers. If in doubt, users should verify with the company itself to avoid any potential issues.
Users should always take a close look at the sender’s display name when checking the legitimacy of an email. Most companies use a single domain for their URLs and emails, so a message that originates from a different domain is a red flag.
As a general rule, users should not click links or download files even if they come from seemingly “trustworthy” sources.
Check for mismatched URLs. While an embedded URL might seem perfectly valid, hovering above it might show a different web address. In fact, users should avoid clicking links in emails unless they are certain that it is a legitimate link.
Users should always be on the lookout for any grammatical errors and spelling mistakes. Legitimate companies will often employ proofreaders and editors who ensure that the materials they send out are error-free.
Users should not be frightened or intimidated by messages that have an alarmist tone. They should double check with the company if they are uncertain about the status of their accounts.
Phishing emails are designed to be sent to a large number of people, so they need to be as impersonal as possible. Users should check whether the message contains a generic subject and greeting, as this can be a sign of a phishing attempt.
Although not every end user has access to advanced anti-phishing software, they can still use the built-in protection of their email clients to filter messages. One example is setting the email client to block all images unless approved.
Legitimate companies will never send confirmation emails unless there are specific reasons for doing so. In fact, most companies will avoid sending unsolicited messages unless it’s for company updates, newsletters, or advertising purposes.
Users should always take the context of an email or message into account. For example, most online accounts do away with viewable member numbers, so users should be wary if they receive emails containing a “member number” for services that generally don’t use them.
It is important to take note of unusual information in the text of the message. Any mentions of operating systems and software that are not typically used by consumers can often be indicators of a phishing attempt.
If it seems suspicious, it probably is. Users should always err on the side of caution when it comes to sending out personally identifiable information through messages and emails.
Link(s):
https://thehackernews.com/2025/03/cert-ua-warns-dark-crystal-rat-targets.html
https://cert.gov.ua/article/6282737