Email-Worm.Win32.Sonic

Class Email-Worm
Platform Win32
Description

Technical Details

This is a multi-component Internet-worm infecting Win32 machines and spreading in e-mail messages as an attached EXE file. The worm has several components, and is able to “upgrade” itself from an Internet Web site.

There are two principal worm components: Loader and Main component.

The Loader is a Windows EXE file about 25K in size (it is compressed by a UPX PE EXE file-compression utility, which being decompressed reaches about 70K in size). When the loader is activated on a computer (being run from e-mail attach),
it registers itself as a hidden process (service), copies itself to the Windows system directory with the name GDI32.EXE, and registers in the auto-run system registry key:

HKLMSoftwareMicrosoftWindowsCurrentVersionRun
GDI = WinSystemGDI32.EXE

where “WinSystem” is the Windows system directory name. As a result, the worm Loader then is executed upon each Windows startup. Note that there are standard Windows components in this directory: GDI.EXE and GDI32.DLL. The
worm uses the GDI32.EXE name to disguise itself in a standard Windows environment.

To hide its activity, the worm then displays the fake error message:

FileName n’ est pas une application Win32 valide.

where FileName is the actual file name the worm was started from.

The worm then activates the main procedure that obtains and executes the Main component. It enters the http://www.geocities.com/olivier1548/ Web page and obtains several files from there:

  • LASTVERSION.TXT – a text file with the number of the latest worm version available there. If there is no new version, the worm exits.
  • nn.ZIP – latest version of worm Main component, “nn” is
    defined in LASTVERSION.TXT.

  • GATEWAY.ZIP – latest version of worm Loader component.

The nn.ZIP and GATEWAY.ZIP files are not actually archives, but an encrypted Windows EXE file. The worm Loader decrypts them, copies to the Windows directory and spawns. As a result, the Main component is activated on the computer.

The Main worm component is the Windows EXE file about 40K in size (it is compressed by a UPX PE EXE file-compression utility, which being decompressed reaches 120K in size). It is installed to the Windows directory with the GDI32A.EXE name and is registered in the system registry in a similar way as
described above for the virus loader. The main components then, depending on some conditions, open the Windows Address Book, obtain Inet addresses from there and send infected e-mail messages. In the known worm version, these messages have:

Subject: Choose your poison
Attached file name: girls.exe

The Main worm component also has Backdoor abilities to watch at infected computer and run its resources from remote host machine.