ServHelper is a new malware family — best classified as a backdoor first observed in the wild in November 2018. Its name is based on a filename (ServHelper.dll).
There are two distinct variants of ServHelper: a “tunnel” variant and a “downloader” variant. The “tunnel” variant has more features and focuses on setting up reverse SSH tunnels to allow the threat actor to access the infected host via Remote Desktop Protocol (RDP). Once ServHelper establishes remote desktop access, the malware contains functionality for the threat actor to “hijack” legitimate user accounts or their web browser profiles and use them as they see fit. The “downloader” variant is stripped of the tunneling and hijacking functionality and is used as a basic downloader.
Both variants of ServHelper use the same HTTP C&C protocol on port 443 (HTTPS) and, less frequently, port 80 (HTTP). An example of the initial phone home to the C&C server.
Exposure of sensitive information
Indicators of Compromise
Malware Hash (MD5/SHA1/SH256)