WORM_CRIDEX.GKL

This worm arrives via removable drives. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It drops copies of itself into all the removable drives connected to an affected system. It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

It connects to certain URLs. It may do this to remotely inform a malicious user of its installation. It may also do this to download possibly malicious files onto the computer, which puts the computer at a greater risk of infection by other threats.

It deletes the initially executed copy of itself.

Arrival Details

This worm arrives via removable drives.

It 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 worm 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:\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 worm 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 worm adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\{random hex string 1}

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\{random hex string 2}

It adds the following registry entries:

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\{random hex string 1}
(Default) = "{hex values}"

Propagation

This worm drops copies of itself into all the removable drives connected to an affected system.

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

The said .INF file contains the following strings:

[autorun]
open={Malware Path and File Name}.exe
shell\Open\Command={Malware Path and File Name}.exe
shell\Open\Default=1
shell\Explore\Command={Malware Path and File Name}.exe
shell\Autoplay\command={Malware Path and File Name}.exe

Download Routine

This worm connects to the following malicious URLs:

• http://{BLOCKED}.{BLOCKED}.140.202:8080/za/v_01_a/in/
• http://{BLOCKED}.{BLOCKED}.194.242:8080/za/v_01_a/in/
• http://{BLOCKED}.{BLOCKED}.134.23:8080/za/v_01_a/in/
• http://{BLOCKED}.{BLOCKED}.214.180:8080/za/v_01_a/in/
• http://{BLOCKED}.{BLOCKED}.5.140:8080/za/v_01_a/in/
• http://{BLOCKED}.{BLOCKED}.150.72:8080/za/v_01_a/in/
• http://{BLOCKED}.{BLOCKED}.206.179:8080/za/v_01_a/in/
• http://{BLOCKED}.{BLOCKED}.23.100:8080/za/v_01_a/in/
• http://{BLOCKED}.{BLOCKED}.164.18:8080/za/v_01_a/in/
• http://{BLOCKED}.{BLOCKED}.204.32:8080/za/v_01_a/in/
• http://{BLOCKED}.{BLOCKED}.179.185:8080/za/v_01_a/in/
• http://{BLOCKED}.{BLOCKED}.189.212:8080/za/v_01_a/in/
• http://{BLOCKED}.{BLOCKED}.49.51:8080/za/v_01_a/in/

Other Details

This worm deletes the initially executed copy of itself

NOTES:

The created registry keys HKEY_CURRENT_USER\Software\Microsoft\Windows NT\{random hex string 1} and HKEY_CURRENT_USER\Software\Microsoft\Windows NT\{random hex string 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 to be deleted since it won't cause the user system any harm.