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BKDR_CRIDEX.LSX

November 19, 2012
 Analysis by: Anthony Joe Melgarejo
 ALIASES:

Worm:Win32/Cridex.E (Microsoft), W32.Cridex (Symantec)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, 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 deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

100,352 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

13 Nov 2012

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:

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

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

It creates the following folders:

  • %User Profile%\Application Data\{random folder name}

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

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 value 1}

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\{random value 2}

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}.189.180:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.238.18:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.61.59:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.237.9:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.172.202:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.102.95:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.221.6:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.220.180:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.221.247:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.238.9:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.215.167:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.213.210:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.89.82:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.187.72:8080/jsbqmCA/hCpyb/Cnw/ED/

It deletes the initially executed copy of itself

NOTES:

It monitors the following browsers:

  • chrome.exe
  • firefox.exe

  SOLUTION

Minimum Scan Engine:

9.300

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.LSX

Step 3

Restart in Safe Mode

[ Learn More ]

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\Microsoft\Windows NT
    • {random value 1}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT
    • {random value 2}

Step 5

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

Step 6

Search and delete this folder

[ 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.
  • %User Profile%\Application Data\{random folder name}

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_CRIDEX.LSX. 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 value 1} and HKEY_CURRENT_USER\Software\Microsoft\Windows NT\{random value 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 keys need not be deleted since it won't cause the user system any harm.


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