Conclusion
We analyzed Linux/CDRThief malware, which has a unique purpose to target specific VoIP softswitches. We rarely see VoIP softswitches targeted by threat actors; this makes the Linux/CDRThief malware interesting.
It’s hard to know the ultimate goal of attackers who use this malware. However, since this malware exfiltrates sensitive information, including call metadata, it seems reasonable to assume that the malware is used for cyberespionage. Another possible goal for attackers using this malware is VoIP fraud. Since the attackers obtain information about activity of VoIP softswitches and their gateways, this information could be used to perform
International Revenue Share Fraud (IRSF).