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BKDR_VAWTRAK.YUYIG

January 22, 2016
 Analysis by: Janus Agcaoili
 ALIASES:

Troj/Vawtrak-DA (Sophos), Backdoor:Win64/Vawtrak.C (Microsoft),

 PLATFORM:

Windows

 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 as an attachment to email messages spammed by other malware/grayware or malicious users.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

367,605 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

20 Jan 2016

Arrival Details

This backdoor arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

Installation

This backdoor drops and executes the following files:

  • %User Temp%\ones.exe
  • %User Temp%\wan.jpg

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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\CurrentVersion\Run
{random value} = '%Application Data%\{random string 1}\{random string 2}.exe"

Other System Modifications

This backdoor 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"

HKEY_CURRENT_USER\Software\{GUID 1}\
{GUID 2}
{random 4 letters} = "{hex values}"

Dropping Routine

This backdoor drops the following files:

  • %Application Data%\{random string 1}\{random string 2}.exe

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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}abel.com/rss/feed/stream
  • http://{BLOCKED}ing.ru/rss/feed/stream
  • http://{BLOCKED}tels.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}ea.com/rss/feed/stream
  • http://{BLOCKED}eselects.com/rss/feed/stream

It deletes the initially executed copy of itself

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

12.280.04

FIRST VSAPI PATTERN DATE:

18 Jan 2016

VSAPI OPR PATTERN File:

12.281.00

VSAPI OPR PATTERN Date:

19 Jan 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

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 value} = '%Application Data%\{random string 1}\{random string 2}.exe"
  • 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"

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.
  • %User Temp%\ones.exe
  • %User Temp%\wan.jpg
  • %Application Data%\{random string 1}\{random string 2}.exe

Step 6

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

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.

HKEY_CURRENT_USER\Software\{random string 1}\{random value}
{random 4 letters} = {hex values}


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