BKDR_VAWTRAK.YUYAMW

April 06, 2017
 ALIASES:

Trojan:Win32/Dynamer!ac (Microsoft); Trojan.Gen.2 (Symantec); Trojan-Spy.MSIL.Omaneat.cgn (Kaspersky); Mal/Generic-L (Sophos); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse Atros5.TPK (AVG)

 PLATFORM:

Windows

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

  • 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.

  TECHNICAL DETAILS

File Size:

1,502,720 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

06 Apr 2017

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:

  • %Program Files%\Microsoft\Rdp.exe

(Note: %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.)

It creates the following folders:

  • %System Root%\Documents and Settings\Wilbert
  • %User Profile%\Microsoft\CLR Security Config
  • %User Profile%\CLR Security Config\v2.0.50727.42
  • %User Profile%\Application Data\Monitor
  • %Program Files%\Microsoft
  • %User Profile%\Monitor\Logs
  • %User Profile%\Monitor\Files
  • %User Profile%\Monitor\Guard
  • %User Profile%\Monitor\Screenshots

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.. %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.)

Other System Modifications

This Backdoor deletes the following files:

  • {malware path and file name}:zone.identifier
  • %Program Files%\Microsoft\Rdp.exe:Zone.Identifier

(Note: %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.)

It adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\MediaResources\msvideo

It adds the following registry entries:

HKEY_CURRENT_USER\Software
/oq78v5N+m08synBpf4WIQ== = "viFgPXKhQKUaHwU4btcFW/C8hmzTbFDQ0/b4vbDvhB4="

HKEY_CURRENT_USER\Software
Wn+UOcpCZJUkqRsj4c6M3g== = "RyAaErux/lUoQqoUcyXRMc8SFobCSc1Ve10hxM/4rsc="

HKEY_CURRENT_USER\Software
hYds8IHRceA+Td4XrRmEAA== = "/dguSIXd2aELxtj69CftB5xaU0VBsfA+TOoOjVbTiqo="

HKEY_CURRENT_USER\Software
Wn+UOcpCZJUkqRsj4c6M3g== = "/Tw45NiKSCenvOdAyHIF8Q=="

HKEY_CURRENT_USER\Software
GxOsNACBb76a9wMokhPO3w== = "v9kF38I0d0wvz4ZtIZtQ8w=="

HKEY_CURRENT_USER\Software
yIthYiKxFv3SDt0uD9iCCYNC2apYR5cKujRvzdfs6S4= = "zxIWhsJJzVV7XSHEz/iuxw=="

HKEY_CURRENT_USER\Software
4GfQogmTTlDPOiK9+JoASc8SFobCSc1Ve10hxM/4rsc= = "zxIWhsJJzVV7XSHEz/iuxw=="

HKEY_CURRENT_USER\Software
IV4VtQwe4+tDfwau1vbAlg== = "{random characters}"

Dropping Routine

This Backdoor drops the following files:

  • %User Profile%\My Documents\Delay.txt
  • %Windows%\Microsoft.NET\Framework\v2.0.50727\config\security.config.cch.new
  • %User Profile%\v2.0.50727.42\security.config.cch.new
  • %Windows%\Microsoft.NET\Framework\v2.0.50727\config\enterprisesec.config.cch.new
  • %User Profile%\Guard\1
  • %User Temp%\8620

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.. %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.. %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.)

Other Details

This Backdoor connects to the following possibly malicious URL:

  • {BLOCKED}.181.87

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.8

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

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_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\MediaResources
    • msvideo

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
    • /oq78v5N+m08synBpf4WIQ== = "viFgPXKhQKUaHwU4btcFW/C8hmzTbFDQ0/b4vbDvhB4="
  • In HKEY_CURRENT_USER\Software
    • Wn+UOcpCZJUkqRsj4c6M3g== = "RyAaErux/lUoQqoUcyXRMc8SFobCSc1Ve10hxM/4rsc="
  • In HKEY_CURRENT_USER\Software
    • hYds8IHRceA+Td4XrRmEAA== = "/dguSIXd2aELxtj69CftB5xaU0VBsfA+TOoOjVbTiqo="
  • In HKEY_CURRENT_USER\Software
    • Wn+UOcpCZJUkqRsj4c6M3g== = "/Tw45NiKSCenvOdAyHIF8Q=="
  • In HKEY_CURRENT_USER\Software
    • GxOsNACBb76a9wMokhPO3w== = "v9kF38I0d0wvz4ZtIZtQ8w=="
  • In HKEY_CURRENT_USER\Software
    • yIthYiKxFv3SDt0uD9iCCYNC2apYR5cKujRvzdfs6S4= = "zxIWhsJJzVV7XSHEz/iuxw=="
  • In HKEY_CURRENT_USER\Software
    • 4GfQogmTTlDPOiK9+JoASc8SFobCSc1Ve10hxM/4rsc= = "zxIWhsJJzVV7XSHEz/iuxw=="
  • In HKEY_CURRENT_USER\Software
    • IV4VtQwe4+tDfwau1vbAlg== = "{random characters}"

Step 4

Search and delete these components

[ Learn More ]
There may be some components 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 Profile%\My Documents\Delay.txt
  • %Windows%\Microsoft.NET\Framework\v2.0.50727\config\security.config.cch.new
  • %User Profile%\v2.0.50727.42\security.config.cch.new
  • %Windows%\Microsoft.NET\Framework\v2.0.50727\config\enterprisesec.config.cch.new
  • %User Profile%\Guard\1
  • %User Temp%\8620

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.
  • %System Root%\Documents and Settings\Wilbert
  • %User Profile%\Microsoft\CLR Security Config
  • %User Profile%\CLR Security Config\v2.0.50727.42
  • %User Profile%\Application Data\Monitor
  • %Program Files%\Microsoft
  • %User Profile%\Monitor\Logs
  • %User Profile%\Monitor\Files
  • %User Profile%\Monitor\Guard
  • %User Profile%\Monitor\Screenshots

Step 6

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

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • {malware path and file name}:zone.identifier
  • %Program Files%\Microsoft\Rdp.exe:Zone.Identifier


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