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TROJ_CRYPCTB.YWF

June 05, 2015
 ALIASES:

Ransom:Win32/Critroni.B (Microsoft); RDN/Ransom!ex (McAfee); Trojan.Gen (Symantec); Trojan-Ransom.Win32.Onion.dt (Kaspersky); Mal/Generic-L (Sophos); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse Crypt_vb.GSK (AVG)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Trojan 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:

217,254 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

02 Jun 2015

Arrival Details

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

Other System Modifications

This Trojan modifies the following file(s):

  • %Application Data%\Microsoft\Windows Media\9.0\WMSDKNS.XML
  • %Application Data%\Microsoft\Windows Media\9.0\WMSDKNS.DTD

(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.)

It deletes the following files:

  • %Application Data%\Microsoft\Windows Media\9.0\WMSDKNSR.XML

(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.)

It adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
MediaPlayer\Health\{F3334A58-7C17-4549-912C-82976C228E0D}

HKEY_CURRENT_USER\Software\Microsoft\
MediaPlayer\Preferences\ProxySettings

HKEY_CURRENT_USER\Software\Microsoft\
MediaPlayer\Preferences\ProxySettings\
MMS

HKEY_CURRENT_USER\Software\Microsoft\
MediaPlayer\Preferences\ProxySettings\
HTTP

HKEY_CURRENT_USER\Software\Microsoft\
MediaPlayer\Preferences\ProxySettings\
RTSP

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows Media\WMSDK\General
UniqueID = "{D25AE8F1-3B56-4234-B943-BC9D1E9823EC}"

HKEY_CURRENT_USER\Software\Microsoft\
Windows Media\WMSDK\General
ComputerName = "CWS11D006"

HKEY_CURRENT_USER\Software\Microsoft\
Windows Media\WMSDK\General
VolumeSerialNumber = "68adfd"

HKEY_CURRENT_USER\Software\Microsoft\
MediaPlayer\Preferences\ProxySettings\
MMS
ProxyStyle = "0"

HKEY_CURRENT_USER\Software\Microsoft\
MediaPlayer\Preferences\ProxySettings\
MMS
ProxyPort = "6db"

HKEY_CURRENT_USER\Software\Microsoft\
MediaPlayer\Preferences\ProxySettings\
MMS
ProxyBypass = "0"

HKEY_CURRENT_USER\Software\Microsoft\
MediaPlayer\Preferences\ProxySettings\
HTTP
ProxyStyle = "1"

HKEY_CURRENT_USER\Software\Microsoft\
MediaPlayer\Preferences\ProxySettings\
HTTP
ProxyPort = "5"

HKEY_CURRENT_USER\Software\Microsoft\
MediaPlayer\Preferences\ProxySettings\
HTTP
ProxyBypass = "0"

HKEY_CURRENT_USER\Software\Microsoft\
MediaPlayer\Preferences\ProxySettings\
RTSP
ProxyStyle = "0"

HKEY_CURRENT_USER\Software\Microsoft\
MediaPlayer\Preferences\ProxySettings\
RTSP
ProxyPort = "22a"

HKEY_CURRENT_USER\Software\Microsoft\
MediaPlayer\Preferences\ProxySettings\
RTSP
ProxyBypass = "0"

HKEY_CURRENT_USER\Software\Microsoft\
MediaPlayer\Player\Tasks\
NowPlaying
InitFlags = "1"

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows Media\WMSDK\Namespace
LocalBase = "%Application Data%\Microsoft\Windows Media\9.0\WMSDKNS.XML"

(Note: The default value data of the said registry entry is %System Root%\Documents and Settings\Default User\Local Settings\Application Data\Microsoft\Windows Media\9.0\WMSDKNS.XML.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows Media\WMSDK\Namespace
DTDFile = "%Application Data%\Microsoft\Windows Media\9.0\WMSDKNS.DTD"

(Note: The default value data of the said registry entry is %System Root%\Documents and Settings\Default User\Local Settings\Application Data\Microsoft\Windows Media\9.0\WMSDKNS.DTD.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows Media\WMSDK\Namespace
LocalDelta = "%Application Data%\Microsoft\Windows Media\9.0\WMSDKNSD.XML"

(Note: The default value data of the said registry entry is %System Root%\Documents and Settings\Default User\Local Settings\Application Data\Microsoft\Windows Media\9.0\WMSDKNSD.XML.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows Media\WMSDK\Namespace
RemoteDelta = "%Application Data%\Microsoft\Windows Media\9.0\WMSDKNSR.XML"

(Note: The default value data of the said registry entry is %System Root%\Documents and Settings\Default User\Local Settings\Application Data\Microsoft\Windows Media\9.0\WMSDKNSR.XML.)

Dropping Routine

This Trojan drops the following files:

  • %Application Data%\Microsoft\Windows Media\9.0\WMSDKNS.XML.bak
  • %Application Data%\Microsoft\Windows Media\9.0\WMSDKNS.XML.done
  • %Application Data%\Microsoft\Windows Media\9.0\WMSDKNSD.XML
  • %Application Data%\Microsoft\Windows Media\9.0\WMSDKNS.XML

(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.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.750

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_CURRENT_USER\Software\Microsoft\MediaPlayer\Health
    • {F3334A58-7C17-4549-912C-82976C228E0D}
  • In HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Preferences
    • ProxySettings
  • In HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Preferences\ProxySettings
    • MMS
  • In HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Preferences\ProxySettings
    • HTTP
  • In HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Preferences\ProxySettings
    • RTSP

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\Windows Media\WMSDK\General
    • UniqueID = "{D25AE8F1-3B56-4234-B943-BC9D1E9823EC}"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows Media\WMSDK\General
    • ComputerName = "CWS11D006"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows Media\WMSDK\General
    • VolumeSerialNumber = "68adfd"
  • In HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Preferences\ProxySettings\MMS
    • ProxyStyle = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Preferences\ProxySettings\MMS
    • ProxyPort = "6db"
  • In HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Preferences\ProxySettings\MMS
    • ProxyBypass = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Preferences\ProxySettings\HTTP
    • ProxyStyle = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Preferences\ProxySettings\HTTP
    • ProxyPort = "5"
  • In HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Preferences\ProxySettings\HTTP
    • ProxyBypass = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Preferences\ProxySettings\RTSP
    • ProxyStyle = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Preferences\ProxySettings\RTSP
    • ProxyPort = "22a"
  • In HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Preferences\ProxySettings\RTSP
    • ProxyBypass = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Player\Tasks\NowPlaying
    • InitFlags = "1"

Step 4

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows Media\WMSDK\Namespace
    • From: LocalBase = "%Application Data%\Microsoft\Windows Media\9.0\WMSDKNS.XML"
      To: LocalBase = ""%System Root%\Documents and Settings\Default User\Local Settings\Application Data\Microsoft\Windows Media\9.0\WMSDKNS.XML""
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows Media\WMSDK\Namespace
    • From: DTDFile = "%Application Data%\Microsoft\Windows Media\9.0\WMSDKNS.DTD"
      To: DTDFile = ""%System Root%\Documents and Settings\Default User\Local Settings\Application Data\Microsoft\Windows Media\9.0\WMSDKNS.DTD""
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows Media\WMSDK\Namespace
    • From: LocalDelta = "%Application Data%\Microsoft\Windows Media\9.0\WMSDKNSD.XML"
      To: LocalDelta = ""%System Root%\Documents and Settings\Default User\Local Settings\Application Data\Microsoft\Windows Media\9.0\WMSDKNSD.XML""
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows Media\WMSDK\Namespace
    • From: RemoteDelta = "%Application Data%\Microsoft\Windows Media\9.0\WMSDKNSR.XML"
      To: RemoteDelta = ""%System Root%\Documents and Settings\Default User\Local Settings\Application Data\Microsoft\Windows Media\9.0\WMSDKNSR.XML""

Step 5

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.
  • %Application Data%\Microsoft\Windows Media\9.0\WMSDKNS.XML.bak
  • %Application Data%\Microsoft\Windows Media\9.0\WMSDKNS.XML.done
  • %Application Data%\Microsoft\Windows Media\9.0\WMSDKNSD.XML
  • %Application Data%\Microsoft\Windows Media\9.0\WMSDKNS.XML

Step 6

Scan your computer with your Trend Micro product to delete files detected as TROJ_CRYPCTB.YWF. 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 deleted/modified files and/or registry entries from backup

*Note: Only Microsoft-related files/keys/values will be restored. If this malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.

    • %Application Data%\Microsoft\Windows Media\9.0\WMSDKNS.XML
    • %Application Data%\Microsoft\Windows Media\9.0\WMSDKNS.DTD

Step 8

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.

  • %Application Data%\Microsoft\Windows Media\9.0\WMSDKNSR.XML


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