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BKDR_CRIDEX.WD

November 30, 2012
 Analysis by: Rhena Inocencio
 Modified by: Anthony Joe Melgarejo
 ALIASES:

Worm:Win32/Cridex.E (Microsoft), W32.Cridex (Symantec), PWS-Zbot.gen.anq (McAfee)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 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.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

92,672 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

23 Nov 2012

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 files:

  • %User Temp%\exp{1 digit number}.exe.tmp

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

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

  • %User Profile%\Application Data\KB{random number}.exe

(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.)

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
KB{random number}.exe = "%User Profile%\Application Data\KB{random number}.exe"

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\{random key name 2}

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\{random key name 1}

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
GlobalUserOffline = "0"

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}.{BLOCKED}.215.210:8080/LvI/xCA/GoZZkCAAAA/Noy6SAAAA/
  • http://{BLOCKED}.{BLOCKED}.59.55:8080/LvI/xCA/GoZZkCAAAA/Noy6SAAAA/
  • http://{BLOCKED}.{BLOCKED}.58.80:8080/LvI/xCA/GoZZkCAAAA/Noy6SAAAA/
  • http://{BLOCKED}.{BLOCKED}.206.66:8080/LvI/xCA/GoZZkCAAAA/Noy6SAAAA/
  • http://{BLOCKED}.{BLOCKED}.150.72:8080/LvI/xCA/GoZZkCAAAA/Noy6SAAAA/
  • http://{BLOCKED}.{BLOCKED}.61.59:8080/LvI/xCA/GoZZkCAAAA/Noy6SAAAA/
  • http://{BLOCKED}.{BLOCKED}.17.180:8080/LvI/xCA/GoZZkCAAAA/Noy6SAAAA/
  • http://{BLOCKED}.{BLOCKED}.100.108:8080/LvI/xCA/GoZZkCAAAA/Noy6SAAAA/
  • http://{BLOCKED}.{BLOCKED}.189.180:8080/LvI/xCA/GoZZkCAAAA/Noy6SAAAA/
  • http://{BLOCKED}.{BLOCKED}.72.46:8080/LvI/xCA/GoZZkCAAAA/Noy6SAAAA/
  • http://{BLOCKED}.{BLOCKED}.187.72:8080/LvI/xCA/GoZZkCAAAA/Noy6SAAAA/
  • http://{BLOCKED}.{BLOCKED}.89.82:8080/LvI/xCA/GoZZkCAAAA/Noy6SAAAA/
  • http://{BLOCKED}.{BLOCKED}.147.52:8080/LvI/xCA/GoZZkCAAAA/Noy6SAAAA/
  • http://{BLOCKED}.{BLOCKED}.5.140:8080/LvI/xCA/GoZZkCAAAA/Noy6SAAAA/

It deletes the initially executed copy of itself

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

9.650.03

FIRST VSAPI PATTERN DATE:

30 Nov 2012

VSAPI OPR PATTERN File:

9.561.00

VSAPI OPR PATTERN Date:

01 Dec 2012

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Scan your computer with your Trend Micro product and note files detected as BKDR_CRIDEX.WD

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\Internet Settings
    • GlobalUserOffline = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • KB{random number}.exe = "%User Profile%\Application Data\KB{random number}.exe"

Step 5

Search and delete the file detected as BKDR_CRIDEX.WD

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files in the search result.

Step 6

Search and delete these files

[ Learn More ]
There may be some component 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%\exp{1 digit number}.exe.tmp

Step 7

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

NOTES:

The created registry keys HKEY_CURRENT_USER\Software\Microsoft\Windows NT\{random key name 1} and HKEY_CURRENT_USER\Software\Microsoft\Windows NT\{random key name 2} cannot be identified by the users since there are no reference values in the created keys. The only way these keys can be identified is by comparing the present keys with a backup if the users have one.

Note that these key need not be deleted since they won't cause the user system any harm.


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