Name :	Virus:W32/Gnil.A
Size:	80,384 bytes
Category:	Malware
Type:	Virus
Platform:	W32
Date of Discovery:	March 08, 2007

Gnil.A has the ability to infect remote computers over a local network and attempts to download and install other malware to the system.

Automatic Disinfection

Usually viruses infecting boot and executable files are automatically disinfected by F-Secure Anti-Virus (FSAV). In some cases, when automatic disinfection is not possible due to file corruption or overwriting virus, a user can select disinfection action by him/herself to make FSAV rename or delete an infected file. In some special cases it is recommended to use specific disinfection tools provided by F-Secure. They can be downloaded from our web or ftp sites:

http://www.f-secure.com/download-purchase/tools.shtml

ftp://ftp.f-secure.com/anti-virus/tools/

F-Secure Anti-Virus can be purchased from our webshop or from our authorised distributors. A trial version F-Secure Anti-Virus, limited to 30 days, can be downloaded from our website:

http://www.f-secure.com/download-purchase/

All the latest versions of FSAV can download anti-virus database updates automatically. However, these updates can be also downloaded and installed manually from our web or ftp sites:

http://www.f-secure.com/download-purchase/updates.shtml

Manual Disinfection

It is not recommended to manually disinfect files and boot sectors from viruses as it can cause damage to a system and make it unbootable.

System Restore issue and file viruses

If Windows ME or XP is used, it is recommended to disable System Restore feature of these operating systems to prevent a computer from re-infection by an already removed malware. The fact is that System Restore feature of these operating systems might save an infected file into the special folder and copy it back to a hard drive it every time it's been renamed or deleted by F-Secure Anti-Virus or by a user. Instructions on how to disable System Restore feature are here:

Windows ME:

http://www.europe.f-secure.com/v-descs/sfc_dis.shtml

Windows XP:

http://www.europe.f-secure.com/v-descs/sfc_dis1.shtml

It is recommended to re-enable System Restore after disinfection in order to restore stable system configuration in the future, if any crash or incompatibility issue occurs.

Gnil.A may arrive in the system as an executable with an icon that depicts an alien.

Sample screenshot:



Once the execution of Gnil.A has been initiated, it will drop the following files into the Windows System directory:


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:


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:


Or it may use the following hard coded path:


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: