Threat behavior
Cutwail is a trojan which is able to download and executes arbitrary files. Downloaded files may be executed from disk or injected directly into another process. Whilst the functionality of the files that are downloaded may change, Cutwail usually downloads a trojan which is able to send spam. Cutwail also employs rootkit and other defensive techniques to avoid detection and removal.
VirTool:WinNT/Cutwail.M is a kernel-mode component used by Cutwail malware family. It contains functionality drop files and to run in Windows safe mode and Windows safe mode with network support.
Installation
VirTool:WinNT/Cutwail.M may be dropped and installed by the TrojanDropper:Win32/Cutwail family. The trojan may be present as a randomly generated alphanumeric file name (e.g. iqw52.sys, Ffn81.sys, etc.) in the following folder:
%SystemRoot%\System32\drivers\
WinNT/Cutwail.M is then launched as a service that runs in Windows safe mode and Windows safe mode with network support.
Payload
Downloads other malware
VirTool:WinNT/Cutwail.M injects and executes a downloader component into a currently running system process such as 'services.exe'. The downloader component may download and execute additional files from a remote server or updates the WinNT/Cutwail.M trojan executable.
Analysis by Shawn Wang
Prevention
