Analysis by: Anthony Joe Melgarejo
ALIASES:

Worm:Win32/Cridex.E (Microsoft), W32/Cridex.NTO!tr (Fortinet), Worm.Win32.Cridex (Ikarus)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • 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 executes then deletes itself afterward.

  TECHNICAL DETAILS

File Size: 252,416 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 16 May 2013

Arrival Details

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

Installation

This backdoor drops the following copies of itself into the affected system and executes them:

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

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

It drops the following files:

  • %User Temp%\exp{random number}.tmp
  • %User Temp%\exp{random number}.tmp.exe
  • %Application Data%\{random}\{random}

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

It creates the following folders:

  • %Application Data%\{random}

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

It executes then deletes itself afterward.

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

Other System Modifications

This backdoor adds the following registry entries:

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

HKEY_CURRENT_USER\Software\Windows NT\
S{random value}
Default = "{random values}"

It adds the following registry keys as part of its installation routine:

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

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

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}.{BLOCKED}.234.53:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.190.170:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.5.195:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.74.5:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.3.246:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}. 38.172:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.224.130:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.246.151:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.148.92:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.242.8:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.130.98:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.6.95:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.184.3:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.156.20:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.22.14:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.148.213:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.30.185:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.189.229:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.201.180:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.80.40:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.143.90:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}. 6.93:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.167.124:8080/jsbqmCA/hCpyb/Cnw/ED/
  • http://{BLOCKED}.{BLOCKED}.90.92:8080/jsbqmCA/hCpyb/Cnw/ED/

  SOLUTION

Minimum Scan Engine: 9.300

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

Restart in Safe Mode

[ Learn More ]

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

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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT
    • C{random value}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT
    • S{random value}

Step 5

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.
  • %Application Data%\{random}

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

Step 7

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


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