Analysis by: jasperm
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

It drops a copy of itself. It also drops a .SYS file detected as BKDR_TDSS.OW.

It creates files in the last sector of the disk.

This Trojan may be dropped by other malware. It may be unknowingly downloaded by a user while visiting malicious websites.

  TECHNICAL DETAILS

File Size: 123,904 bytes
File Type: PE
Memory Resident: No
Initial Samples Received Date: 24 Jan 2011

Arrival Details

This Trojan may be dropped by other malware.

It may be unknowingly downloaded by a user while visiting malicious websites.

Installation

This Trojan drops and executes the following files:

  • %User Temp%\{random}.TMP - SYS file detected as BKDR_TDSS.OW

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003.)

It drops the following copies of itself into the affected system:

  • %User Temp%\{random}.TMP - DLL version

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003.)

Autostart Technique

This Trojan registers its dropped component as a system service to ensure its automatic execution at every system startup. It does this by creating the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random number}
ImagePath = %User Temp%\{random}.TMP

Other Details

This Trojan does the following:

  • It creates the following files in the last sector of the disk:
    • ldr64 - detected as TROJ_TDSS.ANU
    • bckfg.tmp - contains encrypted data
    • cfg.ini - configuration file
    • cmd64 - detected as TROJ_TDSS.KAX
    • cmd.dll - detected as MAL_TDSS-16
    • drv32 - detected as BKDR_TDSS.OW
    • drv64 - detected as s BKDR_TDSS.ANU
    • ldr16 - detected as TROJ_TDSS.ANU
    • ldr32 - detected as TROJ_TDSS.ANU

  SOLUTION

Minimum Scan Engine: 8.900
VSAPI PATTERN File: under testing

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Remove malware files dropped/downloaded by TROJ_TDSS.AJB

    • BKDR_TDSS.OW
    • TROJ_TDSS.ANU
    • TROJ_TDSS.KAX
    • MAL_TDSS-16
    • BKDR_TDSS.ANU

Step 3

Identify and delete files detected as TROJ_TDSS.AJB using either the Startup Disk or Recovery Console

[ Learn More ]

Step 4

Delete this registry key

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

 
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • {malware key}

Step 5

Scan your computer with your Trend Micro product to delete files detected as TROJ_TDSS.AJB. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


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