Tricephalic Hellkeeper Backdoor Alert on Windows Exchange Server

[pronto 6]

Servus Community,

we have received a backdoor alert from a Yara rule scanner (Thor) on both Exchange servers over the past two days. A signature of the backdoor Tricephalic Hellkeeper was found in the process memory[1]. I'm pretty sure this is a false positive detection, as this backdoor appears to have been developed for Linux and Solaris. I have now whitelisted the rule on both Exchange servers.

Finally, I wanted to ask here if there is any other information known about this backdoor that makes the issue more critical than it appears? Here are the files whose processes are affected. All of them have also been tested negatively by Virustotal. ESET has not reported any suspicious behavior either:

• PATH: C:\Program Files\Microsoft\Exchange Server\V15\Bin\MSExchangeHMRecovery.exe
• PATH: C:\Program Files\Microsoft\Exchange Server\V15\Bin\MSExchangeCompliance.exe
• PATH: C:\Program Files\Microsoft\Exchange Server\V15\Bin\Microsoft.Exchange.Mitigation.Service.exe
• PATH: C:\Program Files\Microsoft\Exchange Server\V15\Bin\ComplianceAuditService.exe

[1] https://exatrack.com/public/Tricephalic_Hellkeeper.pdf

Thx & Bye Tom