This type of trojan allows unauthorized parties to use the infected computer as a proxy server to access the Internet anonymously.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
Trojan-Proxy:W32/Grum.A may arrive in the system in a spam e-mail message containing an image that links to the real malware.
Here is the image associated with the message:
This malware is hosted at the following links:
If the user executes the file they are directed to by the spam message, it creates a copy of itself on the user's computer at the following path and filename:
Grum.A uses the following batch file created on the same directory where the malware was to delete the executed copy of itself:
To enable automatic execution upon system boot, it adds the following auto start registry:
- HKCU\\Software\Microsoft\Windows\CurrentVersion\Run Firewall auto setup = %temp%\winlogon.exe
Note: %temp% is the temporary windows folder:
Once installed, Grum.A serves as a proxy server that communicates to the following address:
Commands from the server may include downloading of files and spamming mails.
Grum.A is a kernel malware that hooks several ntdll APIs to hide its file and process.