Analysis by: Cris Nowell Pantanilla

ALIASES:

Backdoor:Win32/Vawtrak.E (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: 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 connects to a website to send and receive information.

  TECHNICAL DETAILS

File Size: 205,232 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 12 Oct 2016
Payload: Connects to URLs/IPs

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 drops the following copies of itself into the affected system and executes them:

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

(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 creates 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.)

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CURRENT_USER\Software\{random}

HKEY_CURRENT_USER\Software\{EDFF5691-F601-41F7-A3B6-CACDFF8B9693}\
{random 1}

It adds the following registry entries:

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

Backdoor Routine

This backdoor connects to the following websites to send and receive information:

  • http://{BLOCKED}.{BLOCKED}.102.164/module/{random}

Other Details

This backdoor does the following:

  • It is capable of the following:
    • Execute files
    • Install Updates
    • List Process
    • Inject to process
    • Download and execute files
  • It injects code to the all running processes except the following:
    • csrss.exe
    • Dbgview.exe
    • lsass.exe
    • lsm.exe
    • services.exe
    • smss.exe
    • svchost.exe
    • taskhost.exe
    • wininit.exe
    • winlogon.exe
  • This backdoor 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
FIRST VSAPI PATTERN FILE: 12.832.08
FIRST VSAPI PATTERN DATE: 12 Oct 2016
VSAPI OPR PATTERN File: 12.833.00
VSAPI OPR PATTERN Date: 13 Oct 2016

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 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\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\Microsoft\Windows\CurrentVersion\Run
    • {random numbers} = "%All Users Profile%\Application Data\{random 1}\{random 2}.exe"

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_CURRENT_USER\Software
    • {random}
  • In HKEY_CURRENT_USER\Software\{EDFF5691-F601-41F7-A3B6-CACDFF8B9693}
    • {random 1}

Step 5

Search and delete these folders

[ 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}

Step 6

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