Virus:W32/Sality.AA is an appending file infector virus that uses an entry point obscuring technique to hide its presence on the system.
The virus attempts to terminate running antivirus programs. It can also download and install additional malware on the system.
The following file may be dropped on the system:
The file is detected as Virus.Win32.Sality.ab.
It will copy itself to removable drives and shared folders as one of the following :
An autorun.inf file will be created on the drive so that the malware will be executed when it is connected to a computer. It also modifies %windir%\SYSTEM.INI by adding the following section :
Once on the system, the virus searches the hard disk (starting with C:\) and infects any files with the following extensions:
It also infects files with .EXE extensions that are referenced as data in the following registry keys:
The virus appends itself by creating a new 73728 bytes sized section named "[random characters]data". The section contains Sality.AA's obfuscated code.
Entry Point Obscuration
On infection, the first 327 bytes from the file's entry point are overwritten with deobfuscation code. If the user executes the infected file, Sality.AA restores the original entry point code and launches the program in order to mask its presence.
When run, Sality.AA creates a mutex to ensure only one instance is running. It then modifies a large range of registry entries. The virus attempts to disable processes and services containing strings related to major antivirus software.
The malware connects to the following website to verify an Internet connection :
The malware may connect to the following sites to download and execute additional malware :
Downloaded files are encrypted. They are unencrypted by the malware to the %temp% folder and executed.
The following URLs may possibly be used to get further instructions:
Creates these mutexes:
Sets these values: