SynAck Ransomware Gets Dangerous 'Doppleganging' Feature

The authors of the SynAck ransomware family appear to have found a way to make the malware considerably more dangerous for enterprises.

Kaspersky Lab this week reported discovering a new version of SynAck that uses a very sophisticated technique called Process Doppelganging to try and evade anti-malware tools. In an advisory this week, Kaspersky Lab researchers said they have observed the new variant being used in limited but highly targeted attacks against organizations in the United States, Germany, Kuwait and Iran.

"Enterprises should be aware that threat actors [have] switched to targeted attacks with ransomware," says Anton Ivanov, lead malware analyst, Kaspersky Lab. "Threat actors are beginning to use custom made ransomware with complicated techniques to bypass security solutions," Ivanov says. 

The authors of the new SynAck version have been using a combination of remote desktop protocol brute-force attacks and manual downloads to install the malware on vulnerable systems. The ransomware is designed to encrypt office documents, multimedia files, and database files.

Ransom amounts associated with the new variant have tended to average $3,000, which is a somewhat modest amount considering the sophistication behind the malware and the targeted nature of the campaign. That suggests that the threat actor behind the new SynAck is hoping to make money through volume infections rather than by attempting to extort large sums of money from a small number of victims.

The SynAck version is the first ransomware sample to use the Doppelganging Process, which basically involves a way to run malicious code in the guise of a harmless and legitimate Windows process. Security vendor enSilo demonstrated the technique at Black Hat Europe 2017 last December.

enSilo has described Process Doppelganging as a fileless evasion technique for bypassing real-time file scanning by most AV software and next generation AV tools for all versions of Windows since Windows Vista. Unlike malware that has to be written to disk or run completely from memory, with Process Doppelganging, threat actors can build malware that can run from what appears to be a completely legitimate-looking file.

"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," Kaspersky Lab security researchers said in their advisory. The technique allows attackers to run malicious code without leaving any trace behind, making intrusions extremely hard to detect.

Doppelganging is not the only feature that sets the new SynAck variant apart from other ransomware tools.

Other notable features of the variant include the manner in which the malware obfuscates its executable code before compilation. Instead of using a custom packer to protect the malware code, the new SynAck version obfuscates the executable before compilation, thereby making it significantly harder for security researchers to reverse-engineer the code.

SynAck's latest version also can detect whether it's being launched from an automated sandbox: if so, it will promptly exit the sandbox. Before it actually begins to encrypt files, SynAck also checks the hashes of all processes that are running on the compromised machine, and tries to kill any processes that match a list of processes hard-coded into the malware.

Processes that SynAck is designed to kill include virtual machines, database applications, backup systems, and gaming applications in what appears to be a bid to make it easier to seize high-value files which may otherwise be tied to a running process, Kaspersky Lab said in its report.

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