Threat Descriptions

Trojan-Downloader:W32/Small.AAFH

Classification

Category :

Malware

Type :

Trojan-Downloader

Platform :

W32

Aliases :

Trojan-Downloader:W32/Small.AAFH, Trojan-Downloader:W32/Small.AAFH, Trojan-Downloader.Win32.Small.aafh

Summary

This type of trojan secretly downloads malicious files from a remote server, then installs and executes the files.

Removal

Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.

A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:

  • Check for the latest database updates

    First check if your F-Secure security program is using the latest updates, then try scanning the file again.

  • Submit a sample

    After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.

    Note: If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.

  • Exclude a file from further scanning

    If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.

    Note: You need administrative rights to change the settings.

Technical Details

This trojan is designed to 'persuade' unsuspecting individuals into buying the full, paid version of a rogue antispyware program by spooking them into believing that their system is riddled with malware. The frightened user would then be asked to buy the rogue antispyware program to deal with the supposed problem.This malware arrives as a link in an email and requires user action in order to be installed. The user must click on the link, then download and run or install the malware. It can also be downloaded from a number of websites, such as:

  • http://neonbible.de/[...]/update.exe
  • http://www.intertopo.be/[...]/update.exe
  • http://www.dennis-luis.de/[...]/update.exe
  • http://www.aouq22.dsl.pipex.com/[...]/update.exe

The malware will use a variety of tricks to alarm the user. These tricks involve changing the wallpaper to a 'Spyware Infection warning' wallpaper and changing the user's screensaver into a screensaver which looks like the 'blue screen of death'. The trojan will also attempt to connect to a remote server and download what appears to be a GIF file, which is embedded with the trial version of a rogue antispyware program detected as Rogue:W32/AntivirusXP2008.E. This rogue antispyware program is installed and pretends to run a scan of the infected system, then displays a fake results screen showing numerous infections.Once installed, this trojan removes all the current System Restore points in the system and creates a new one where it is already included. This means that rolling back to a previous System Restore point will not remove the malware.Upon installation into the system, the wallpaper will be changed to this:

Leaving the system idle for 10 minutes brings up a screensaver which appears to be a 'blue screen of death' similar to this one:

When Rogue:W32/AntivirusXP2008.E executes, it will show this window:

File System Changes

Creates these files:

  • phcgqgj0ej7p.bmp
  • tt1.tmp.vbs
  • blphcgqgj0ej7p.scr
  • lphcgqgj0ej7p.exe

Process Changes

Creates these mutexes:

  • {A56DECD8-1102-49e9-BFD5-17FBE35197F2}

Network Connections

Attempts to download files from:

  • Http://antivirusxp-08.com/images/1215432116/[...]dd6a773d899336c058fb89fce801/f7ec4038-ac37-4724-8dc3-f4029fa668f9.gif

Registry Modifications

Sets these values:

  • HKLM\Software\Microsoft\Software Notifier InstallationID = f7ec4038-ac37-4724-8dc3-f4029fa668f9
  • HKCU\Control Panel\Colors Background = 0 0 255
  • HKCU\Control Panel\Desktop WallpaperStyle = 0
  • HKCU\Control Panel\Desktop TileWallpaper = 0
  • HKCU\Control Panel\Desktop Wallpaper = C:\WINDOWS\system32\phcgqgj0ej7p.bmp
  • HKCU\Control Panel\Desktop OriginalWallpaper = C:\WINDOWS\system32\phcgqgj0ej7p.bmp
  • HKCU\Control Panel\Desktop ConvertedWallpaper = C:\WINDOWS\system32\phcgqgj0ej7p.bmp
  • HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System NoDispBackgroundPage = 00000001
  • HKLM\Software\Microsoft\Windows\CurrentVersion\Run lphcgqgj0ej7p = C:\WINDOWS\system32\lphcgqgj0ej7p.exe
  • HKCU\Control Panel\Desktop SCRNSAVE.EXE = C:\WINDOWS\system32\blphcgqgj0ej7p.scr
  • HKCU\Control Panel\Desktop ScreenSaveActive = 1
  • HKCU\Control Panel\Desktop ScreenSaveTimeOut = 600
  • HKCU\Software\Sysinternals\Bluescreen Screen Saver EulaAccepted = 00000001
  • HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System NoDispScrSavPage = 00000001
  • HKLM\System\CurrentControlSet\Services\srservice Start = 00000002
  • HKLM\System\CurrentControlSet\Services\sr Start = 00000000
  • HKLM\System\CurrentControlSet\Services\sr ImagePath = system32\DRIVERS\sr.sys
  • HKLM\Software\Microsoft\Windows NT\CurrentVersion\SystemRestore DisableSR = 00000000