Trojan-Downloader.Win32.SmallOFF : Recognize Attack Patterns and Solutions

ALIASES:

Trojan-Downloader.Win32.SmallOFF (Morbite); TrojanDownloader:Win32/Small.gen!AO (Microsoft); Downloader-BNM.dr (McAfee); Suspicious.DLoader (Symantec); Trojan-Downloader.Win32.Agent.bjum (Kaspersky); Trojan-Downloader.Win32.Agent.oxo (v) (Sunbelt); Trojan.Downloader.JLSE (FSecure)

  PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

  OVERALL RISK RATING:

  DAMAGE POTENTIAL:

  DISTRIBUTION POTENTIAL:

  REPORTED INFECTION:

• 
  Threat Type: Trojan
• 
  Destructiveness: No
• 
  Encrypted:
• 
  In the wild: Yes

Threat behavior

Trojan-Downloader.Win32.SmallOFF (Morbit) is a program that silently downloads and executes arbitrary files without the affected user’s consent. Installation details and the files downloaded and executed may vary from instance to instance because of the generic nature of the detection.

 

For example, one such file detected as Trojan-Downloader.Win32.SmallOFF displayed the following characteristics:

 

It was distributed as a Win32 packed executable of 28,672 bytes in size.

When executed this trojan performs the following actions:

• Attempts to download and execute a file located at IP 70.147.30.110 (at the time of writing this remote file was not available). If successful the trojan stores the downloaded file locally as %windir%\system svchots.exe. (Note the filename difference from the standard windows file svchost.exe). This file is then executed.
• Drops the file %windir%\sysreq2.txt. The trojan uses this file to store the number of successful downloading attempts. The number is in ASCII format (for instance number 1 is represented by hex value 31h).
• Attempts to terminate the running process 'msconf.exe', which is normally associated with other malicious programs.

Arrival Details

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Other System Modifications

This Trojan deletes the following files:

• %Temp%\scs1.tmp
• %Temp%\scs2.tmp

(Note: %Temp% is the Windows temporary folder, where it usually is C:\Windows\Temp on all Windows operating system versions.)

Dropping Routine

This Trojan drops the following files:

• %Windows%\foto2008.jpg
• %System%\Explorer.exe

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.. %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

Other Details

This Trojan connects to the following possibly malicious URL:

• http://fotos.{BLOCKED}o.pt/gentlevip/pic/000200p9/s500x500
• http://olocooco2008xx.{BLOCKED}m.su/eclipse2008.jpg
• http://olocooco2008xx.{BLOCKED}m.su/autoorkut.jpg
• http://www.{BLOCKED}btown.com/rogercdr01/tela3.jpg
• http://www.{BLOCKED}g.com/blogfiles/1/137955/general/msn.exe

This report is generated via an automated analysis system.

Solution

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Search and delete these components

There may be some components that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.

• %Windows%\foto2008.jpg
• %System%\Explorer.exe

To manually delete a malware/grayware file from an affected system:

• For Windows 2000, Windows XP, and Windows Server 2003:

1. Right-click Start then click Search....
2. In the File name* input box, type the following:
   
   • %Windows%\foto2008.jpg
   • %System%\Explorer.exe
3. In the Look In drop-down list, select My Computer then press Enter.
4. Once located, select the file then press SHIFT+DELETE to delete it.
   *Note: The file name input box title varies depending on the Windows version (e.g. Search for files or folders named or All or part of the file name.).

• For Windows Vista, Windows 7, Windows Server 2008, Windows 8, Windows 8.1, and Windows Server 2012:

1. Open a Windows Explorer window.
   • For Windows Vista, 7, and Server 2008 users, click Start>Computer.
   • For Windows 8, 8.1, and Server 2012 users, right-click on the lower left corner of the screen,then click File Explorer.
2. In the Search Computer/This PC input box, type:
   
   • %Windows%\foto2008.jpg
   • %System%\Explorer.exe
3. Once located, select the file then press SHIFT+DELETE to delete it.
   *Note: Read the following Microsoft page if these steps do not work on Windows 7.