BKDR_CRIDEX.DIX

 Analysis by: Rika Joi Gregorio

 ALIASES:

Worm:Win32/Cridex.E(Microsoft), W32.Cridex(Symantec), PWS-Zbot.gen.anm(McAfee), W32/Zbot.AAO!tr(Fortinet), a variant of Win32/Injector.AAAO trojan(Eset)

 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:
 INFORMATION EXPOSURE:

  • 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 is injected into all running processes to remain memory resident.

It does not have any propagation routine.

It executes commands from a remote malicious user, effectively compromising the affected system.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

121,344 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

11 Dec 2012

Payload:

Compromises system security, 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:

  • %Application Data%\KB{random digit}.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 creates the following folders:

  • %Application Data%\BF9BD00E

(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 is injected into all running processes to remain memory resident.

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • Local\XMM{8 random characters}
  • Local\XME{8 random characters}
  • Local\XMI{8 random characters}
  • Local\XMS{8 random characters}
  • Local\XMF{8 random characters}
  • Local\XMR{8 random characters}
  • Local\XMQ{8 random characters}
  • Local\XMB{8 random characters}

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

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CD184B802

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\SBF9BD00E

It adds the following registry entries:

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

Propagation

This backdoor does not have any propagation routine.

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Monitor browser cookies
  • Download and execute arbitrary files
  • Upload stolen information
  • Download configuration files

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://{BLOCKED}.{BLOCKED}.61.59:8080/{random}
  • http://{BLOCKED}.{BLOCKED}.229.36:8080/{random}
  • http://{BLOCKED}.{BLOCKED}.221.135:8080/{random}
  • http://{BLOCKED}.{BLOCKED}.174.136:8080/{random}
  • http://{BLOCKED}.{BLOCKED}.150.72:8080/{random}
  • http://{BLOCKED}.{BLOCKED}.215.194:8080/{random}
  • http://{BLOCKED}.{BLOCKED}.147.52:8080/{random}
  • http://{BLOCKED}.{BLOCKED}.226.157:8080/{random}
  • http://{BLOCKED}.{BLOCKED}.243.18:8080/{random}
  • http://{BLOCKED}.{BLOCKED}.221.247:8080/{random}
  • http://{BLOCKED}.{BLOCKED}.23.100:8080/{random}
  • http://{BLOCKED}.{BLOCKED}.174.122:8080/{random}
  • http://{BLOCKED}.{BLOCKED}.221.6:8080/{random}
  • http://{BLOCKED}.{BLOCKED}.193.112:8080/{random}
  • http://{BLOCKED}.{BLOCKED}.89.82:8080/{random}
  • http://{BLOCKED}.{BLOCKED}.61.66:8080/{random}
  • http://{BLOCKED}.{BLOCKED}.237.170:8080/{random}
  • http://{BLOCKED}.{BLOCKED}.242.217:8080/{random}
  • http://{BLOCKED}.{BLOCKED}.229.36:8080/{random}

Other Details

This backdoor deletes itself after execution.

NOTES:

When this malware successfully connects to its C&C server, it can download configuration files wherein it is saved in the following registries:

HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CD184B802

HKEY_CURRENT_USER\Software\Microsoft\Windows NT\SBF9BD00E

The configuration file may contain information which is used to monitor browser activities, specifically the address bar or title, of the affected system. However, as of this writing, the mentioned sites above were already inaccessible.

It does not have rootkit capabilities.

It does not exploit any vulnerability.

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

10.480.04

FIRST VSAPI PATTERN DATE:

18 Dec 2013

VSAPI OPR PATTERN File:

10.481.00

VSAPI OPR PATTERN Date:

19 Dec 2013

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 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
    • CD184B802
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT
    • SBF9BD00E

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

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.
  • %Application Data%\BF9BD00E

Step 6

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