Analysis by: David John Agni

ALIASES:

Backdoor:Win32/Vawtrak.O (Microsoft)

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Dropped by other malware, Downloaded from the Internet

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 executes commands from a remote malicious user, effectively compromising the affected system.

  TECHNICAL DETAILS

File Size: 192,724 bytes
File Type: DLL
Memory Resident: Yes
Initial Samples Received Date: 23 Dec 2015
Payload: Connects to URLs/IPs, Steals information

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.

Installation

This backdoor adds the following folders:

  • %All Users Profile%\Application Data\{random 1}

(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.)

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

  • %All Users Profile%\Application Data\{random 1}\{random 2}.dll

(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.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersHKEY_CURRENT_USER\Software\
Microsoft\Windows\CurrentVersion\
Runion\Run
{random numbers} = regsvr32.exe "%All Users Profile%\Application Data\{random 1}\{random 2}.dll"

Other System Modifications

This backdoor adds the following registry entries:

HKEY_CURRENT_USER\Software\{CLSID 1}\
{random 1}\{numbers}
{random value 1} = "{hex values}"

HKEY_CURRENT_USER\Software\{CLSID 1}\
{random 1}\{numbers}
{random value 2} = "{hex values}"

HKEY_CURRENT_USER\Software\{CLSID 1}\
{random 1}\{numbers}
{random value 3} = "{hex values}"

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Open a process
  • Install Updates
  • List Running Processes
  • Inject code to process
  • Download and execute files
  • Download configuration

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://{BLOCKED}abel.com/rss/feed/stream
  • http://{BLOCKED}ing.ru/rss/feed/stream`
  • http://{BLOCKED}wear.net/rss/feed/stream
  • http://{BLOCKED}tels.net/rss/feed/stream
  • http://{BLOCKED}lliance.net/rss/feed/stream
  • http://{BLOCKED}trend.com/rss/feed/stream
  • http://{BLOCKED}ia.ru/rss/feed/stream
  • http://{BLOCKED}hone.com/rss/feed/stream
  • http://{BLOCKED}.net/rss/feed/stream
  • http://{BLOCKED}ea.com/rss/feed/stream
  • http://{BLOCKED}eselects.com/rss/feed/stream
  • http://{BLOCKED}ick.net/rss/feed/stream

As of this writing, the said sites are inaccessible.

NOTES:

This backdoor injects code to the all running processes except the following:

  • csrss.exe
  • smss.exe
  • wininit.exe
  • services.exe
  • svchost.exe
  • lsass.exe
  • lsm.exe
  • winlogon.exe
  • Dbgview.exe
  • taskhost.exe

It only performs its intended routine once it is injected in the following processes:

  • chrome.exe
  • explorer.exe
  • firefox.exe
  • iexplore.exe

  SOLUTION

Minimum Scan Engine: 9.800
VSAPI OPR PATTERN File: 12.227.00
VSAPI OPR PATTERN Date: 23 Dec 2015

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

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

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 numbers} = regsvr32.exe "%All Users Profile%\Application Data\{random 1}\{random 2}.dll"

Step 5

Reset Internet security settings

[ Learn More ]

Step 6

Reset Internet privacy settings

[ Learn More ]

Step 7

The following created files/folders/registry keys/registry entries cannot be identified by the user since there are no reference values in the created key. The only way it can be identified is by comparing the present system information with a backup. Note that the said components do not have to be deleted since it won't be harmful to the system.

  • In HKEY_CURRENT_USER\Software\{CLSID 1}\{random 1}\{numbers}
    • {random value 1} = "{hex values}"
  • In HKEY_CURRENT_USER\Software\{CLSID 1}\{random 1}\{numbers}
    • {random value 2} = "{hex values}"
  • In HKEY_CURRENT_USER\Software\{CLSID 1}\{random 1}\{numbers}
    • {random value 3} = "{hex values}"

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_VAWTRAK.AAAFV. 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 9

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %All Users Profile%\Application Data\{random 1}


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