ALIASES:

TrojanDownloader:Win32/Vawtrak.A (Microsoft); Troj/DwnLdr-LCG (Sophos)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet

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.

It executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size: 45,056 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 03 Oct 2013
Payload: Connects to URLs/IPs

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.

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random letters} = "regsvr32.exe /s "%All Users Profile%\Application Data\{random letters}.dat""

Download Routine

This Trojan connects to the following website(s) to download and execute a malicious file:

  • http://{BLOCKED}.{BLOCKED}.188.89/ld/stat.dat

It saves the files it downloads using the following names:

  • %All User Profile%\Application Data\{random letters}.dat - detected as BKDR_VAWTRAK.B

It then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

Other Details

This Trojan deletes itself after execution.

NOTES:

This Trojan checks for the presence of the following security-related sub-folders in the Program Files and %All Users Profile%\Application Data folders:

  • a-squared Anti-Malware
  • a-squared HiJackFree
  • Agnitum
  • Alwil Software
  • AnVir Task Manager
  • ArcaBit
  • AVAST Software
  • AVG
  • avg8
  • Avira
  • Avira GmbH
  • BitDefender
  • BlockPost
  • DefenseWall
  • DefenseWall HIPS
  • Doctor Web
  • DrWeb
  • ESET
  • F-Secure
  • F-Secure Internet Security
  • FRISK Software
  • G DATA
  • K7 omputing
  • Kaspersky Lab
  • Kaspersky Lab Setup Files
  • Lavasoft
  • Malwarebytes
  • Malwarebytes' Anti-Malware
  • McAfee
  • McAfee.com
  • Microsoft Antimalware
  • Microsoft Security Client
  • Microsoft Security Essentials
  • Norton AntiVirus
  • Online Solutions
  • P Tools
  • P Tools Internet Security
  • Panda Security
  • Positive Technologies
  • Sandboxie
  • Security Task Manager
  • Spyware Terminator
  • Sunbelt Software
  • Symantec
  • Symantec Shared
  • Trend Micro
  • UAenter
  • Vba32
  • XORE
  • Zillya Antivirus

Once found, it creates the following registry entries to prevent execution of the security and anti-malware related applications:

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Safer\CodeIdentifiers\0\Paths\{Generated GUID}
ItemData = "{Software path}"
SaferFlags = "0"

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 10.314.09
FIRST VSAPI PATTERN DATE: 02 Oct 2013

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

Remove the malware/grayware file dropped/downloaded by TROJ_DLOADR.AAJ

    • BKDR_VAWTRAK.B

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Delete this registry value

[ 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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random letters} = "regsvr32.exe /s "%All Users Profile%\Application Data\{random letters}.dat""
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Safer\CodeIdentifiers\0\Paths\{Generated GUID}
    • ItemData = {AV Software Path}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Safer\CodeIdentifiers\0\Paths\{Generated GUID}
    • SaferFlags = 0

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_DLOADR.AAJ. 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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