Kaspersky Lab researchers have discovered a new variant of the SynAck ransomware Trojan using the Doppelgänging technique to bypass anti-virus security by hiding in legitimate processes. This is the first time the Doppelgänging technique has been seen in ransomware in the wild. The developers behind SynAck also implement other tricks to evade detection and analysis: obfuscating all malware code prior to sample compilation and exiting if signs suggest it is being launched in a sandbox.
The SynAck ransomware has been known since the autumn of 2017, and in December was observed targeting mainly English-speaking users with remote desktop protocol (RDP) brute-force attacks followed by the manual download and installation of malware. The new variant uncovered by Kaspersky Lab researchers implements a far more sophisticated approach, using the Process Doppelgänging technique to evade detection.
Reported in December 2017, Process Doppelgänging involves a fileless code injection that takes advantage of a built-in Windows function and an undocumented implementation of the Windows process loader. By manipulating how Windows handles file transactions, attackers can pass off malicious actions as harmless, legitimate processes, even if they are using known malicious code. Doppelgänging leaves no traceable evidence behind, making this type of intrusion extremely difficult to detect. This is the first time ransomware has been observed using this technique in-the-wild.
Researchers believe attacks using this new variant of SynAck are highly targeted. To date, they have observed a limited number of attacks in the U.S., Kuwait, Germany, and Iran, with ransom demands of $3,000 USD.
“The race between attackers and defenders in cyberspace is a never-ending one. The ability of the Process Doppelgänging technique to sneak malware past the latest security measures represents a significant threat; one that has, not surprisingly, quickly been seized upon by attackers. Our research shows how the relatively low profile targeted ransomware SynAck used the technique to upgrade its stealth and infection capability. Fortunately, the detection logic for this ransomware was implemented before it appeared in the wild,” said Anton Ivanov, Lead Malware Analyst, Kaspersky Lab.