A threat group tracked as Stantinko was observed using a new version of a Linux proxy Trojan that poses as Apache servers to remain undetected.
Initially detailed in 2017, Stantinko is believed to have been operating since at least 2012, ensnaring infected systems into a botnet mainly used in massive adware campaigns, but also for backdoor activities, brute-force attacks, and more.
Previously, the Stantinko group was mainly known for the targeting of Windows systems, but recent attacks show that they are also focusing on evolving their Linux malware, with a new proxy Trojan that masquerades as httpd, the Apache Hypertext Transfer Protocol Server found on many Linux servers.
“We believe this malware is part of a broader campaign that takes advantage of compromised Linux servers,” Intezer’s security researchers say.
Detected by a single anti-virus engine on VirusTotal, the sample is an unstripped 64-bit ELF binary that, upon execution, validates a configuration file. Should this file be missing or lack the expected structure, the malware stops execution.
If the validation passes, the proxy daemonizes itself, after which it creates a socket and a listener, which enable it to accept connections. According to Intezer, this might be the manner in which infected machines communicate with one another.
The new version, which was identified nearly three years after the previous one, has a similar purpose but shows a series of changes, including the command and control (C&C) IP address being stored in the configuration file dropped alongside the malware, the lack of self-update capabilities in the new version, and the fact that the new version is dynamically linked.
Several function names within the sample were found to be identical with the previous version, yet they are not called statically in the new version. Furthermore, the C&C paths hint at previous campaigns by the same group, suggesting that the new Trojan is indeed linked to Stantinko.