Gnil.A has the ability to infect remote computers over a local network and attempts to download and install other malware to the system.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
Gnil.A may arrive in the system as an executable with an icon that depicts an alien.
Once the execution of Gnil.A has been initiated, it will drop the following files into the Windows System directory:
- xrtnyo.exe - Loader of the .dll component
- xrtnyo.dll - Contains most of the payload
It will delete the executed copy of itself with the help of a batch file created in the temporary folder:
Gnil.A injects its .DLL component to the following processes:
It terminates the following processes related to Viking and Fujacks variants:
Note: String comparison is case sensitive.
It infects binary files of the following extension:
Moreover Gnil.A also infects script files with the following extension:
It avoids infecting folders with the following strings:
- ComPlus Applications
- Common Files
- Internet Explorer
- Microsoft Frontpage
- Movie Maker
- Online Services
- Outlook Express
- System Volume Information
- Windows Media Player
- Windows NT
Note: String comparison is case sensitive. This is why most system files are still infected.
Gnil.A will append a code at the end of the script file to point to a malicious website:
Note: As of this writing the site is no longer available
Gnil.A may also use Internet Explorer to download from the said site. It gets the location of Internet Explorer by querying the following registry entry:
- HKLM\Software\Microsoft\Windows\CurrentVersion\App Paths\IEXPLORE.EXE
Or it may use the following hard coded path:
- C:\Program Files\Internet Explorer\IEXPLORE.EXE
Aside from infecting binary and script files as a way to propagate, it can also spread via network shares using a combination of the following strings as username and passwords: