BKDR_CRIDEX.WD
Worm:Win32/Cridex.E (Microsoft), W32.Cridex (Symantec), PWS-Zbot.gen.anq (McAfee)
Windows 2000, Windows XP, Windows Server 2003
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
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
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
Step 4
Delete this registry value
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"
- GlobalUserOffline = "0"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- KB{random number}.exe = "%User Profile%\Application Data\KB{random number}.exe"
- KB{random number}.exe = "%User Profile%\Application Data\KB{random number}.exe"
Step 5
Search and delete the file detected as BKDR_CRIDEX.WD
Step 6
Search and delete these files
- %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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