Recent Waterbug activity can be divided into three distinct campaigns, characterized by differing toolsets. One campaign involved a new and previously unseen backdoor called Neptun (Backdoor.Whisperer). Neptun is installed on Microsoft Exchange servers and is designed to passively listen for commands from the attackers. This passive listening capability makes the malware more difficult to detect. Neptun is also able to download additional tools, upload stolen files, and execute shell commands.
A second campaign used Meterpreter, a publicly available backdoor along with two custom loaders, a custom backdoor called photobased.dll, and a custom Remote Procedure Call (RPC) backdoor. Waterbug has been using Meterpreter since at least early 2018 and, in this campaign, used a modified version of Meterpreter, which was encoded and given a .wav extension in order to disguise its true purpose.
The third campaign deployed a different custom RPC backdoor to that used in the second campaign. This backdoor used code derived from the publicly available PowerShellRunner tool to execute PowerShell scripts without using powershell.exe. This tool is designed to bypass detection aimed at identifying malicious PowerShell usage. Prior to execution, the PowerShell scripts were stored Base64-encoded in the registry. This was probably done to avoid them being written to the file system.
Indicators of Compromise
IP(s) / Hostname(s)
Malware Hash (MD5/SHA1/SH256)