BKDR_VAWTRAK.AM

 Modified by: Michael John Marcos

 ALIASES:

HEUR:Trojan.Win32.Generic (Kaspersky); Backdoor.Win32.Vawtrak.ab (v) (Sunbelt); Trojan horse PSW.Generic11.CBJQ (AVG)

 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: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

264,206 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

01 May 2014

Arrival Details

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

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random file name} = "regsvr32.exe /s "%Program Data%\{random file name}.dat"" - for Windows Vista and Windows 7

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CURRENT_USER\SOFTWARE\AppDataLow\
{random key 1}

HKEY_CURRENT_USER\SOFTWARE\AppDataLow\
{random key 2}

It adds the following registry entries:

HKEY_LOCAL_MACHINE\Policies\Microsoft\
Windows\Safer\CodeIdentifiers
DefaultLevel = "262144"

HKEY_LOCAL_MACHINE\Policies\Microsoft\
Windows\Safer\CodeIdentifiers
TransparentEnabled = "1"

HKEY_LOCAL_MACHINE\Policies\Microsoft\
Windows\Safer\CodeIdentifiers
PolicyScope = "0"

HKEY_CURRENT_USER\SOFTWARE\AppDataLow\
{random key 2}
{random} = "{random}"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
NoProtectedModeBanner = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
TabProcGrowth = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings\
Zones\3
2500 = "3"

Dropping Routine

This backdoor drops the following files:

  • %All Users Profile%\Application Data\{random file name}.dat
  • %Program Data%\{random file name}.dat - for Windows Vista and Windows 7

(Note: %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}.{BLOCKED}.188.50
  • http://{BLOCKED}.{BLOCKED}.56.247
  • http://{BLOCKED}n.com.tw
  • http://{BLOCKED}g.com.tw

It deletes itself after execution.

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

10.766.03

FIRST VSAPI PATTERN DATE:

01 May 2014

VSAPI OPR PATTERN File:

10.767.00

VSAPI OPR PATTERN Date:

01 May 2014

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

Restart in Safe Mode

[ Learn More ]

Step 3

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_CURRENT_USER\SOFTWARE\AppDataLow
    • {random key 1}
  • In HKEY_CURRENT_USER\SOFTWARE\AppDataLow
    • {random key 2}

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_LOCAL_MACHINE\Policies\Microsoft\Windows\Safer\CodeIdentifiers
    • DefaultLevel = "262144"
  • In HKEY_LOCAL_MACHINE\Policies\Microsoft\Windows\Safer\CodeIdentifiers
    • TransparentEnabled = "1"
  • In HKEY_LOCAL_MACHINE\Policies\Microsoft\Windows\Safer\CodeIdentifiers
    • PolicyScope = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
    • NoProtectedModeBanner = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
    • TabProcGrowth = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3
    • 2500 = "3"
  • In HKEY_CURRENT_USER\SOFTWARE\AppDataLow\{random key 2}
    • {random} = "{random}"
  • In HKEY_CURRENT_USER\Microsoft\Windows\CurrentVersion\Run
    • {random file name} = "regsvr32.exe /s "%All Users Profile%\Application Data\{random file name}.dat""
  • In HKEY_CURRENT_USER\Microsoft\Windows\CurrentVersion\Run
    • "regsvr32.exe /s "%Program Data%\{random file name}.dat""  - for Windows Vista and Windows 7

Step 5

Search and delete this file

[ Learn More ]
There may be some files 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.
  • %All Users Profile%\Application Data\{random file name}.dat
  • %Program Data%\{random file name}.dat

Step 6

Scan your computer with your Trend Micro product to delete files detected as BKDR_VAWTRAK.AM. 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.

Step 7

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