A Russian threat group named ColdRiver, which is known for its phishing attacks, has also been developing custom malware, Google warned on Thursday.
The internet giant has shared indicators of compromise (IoCs) and YARA rules to help defenders detect and analyze the threat.
ColdRiver is tracked by other companies as Star Blizzard, Callisto Group, BlueCharlie, TA446, and Dancing Salome. The group has been linked to a unit of Russia’s FSB security service and is known for conducting both cyberespionage operations and influence campaigns.
The hackers typically target organizations in the academia, defense, government, NGO and think tank sectors in the US, the UK and other NATO countries.
Many of ColdRiver’s attacks involved spear-phishing aimed at credential harvesting. However, Google’s security researchers recently came across custom malware that appears to have been developed and used by the threat actor.
Named Spica, the malware has been described as a backdoor written in Rust that uses JSON over websockets for command and control (C&C). Spica can be used to execute arbitrary shell commands, steal web browser cookies, upload and download files, obtain filesystem contents, and exfiltrate documents.
The malware has been delivered by sending targets benign PDFs that appear to be encrypted. When the victim informs the sender that the PDF is encrypted, they are provided an executable that can allegedly be used to decrypt the document. This executable deploys the malware.
Spica was spotted in the wild by Google in September 2023, but it may have been used by ColdRiver since at least November 2022. The company’s researchers were only able to obtain a single sample of the malware, which they believe may have been used in August and September 2023.
“We believe there may be multiple versions of the SPICA backdoor, each with a different embedded decoy document to match the lure document sent to targets,” Google researchers said.