WORM_CRIDEX.IC

This malware intercepts browser requests and changes the displayed content according to the configuration, written by the administrator of the botnet. This way, cybercriminals can trick users into entering valuable information without raising suspicion. It was also found to generate several random domains using domain generating algorithms (DGA).

To get a one-glance comprehensive view of the behavior of this Worm, refer to the Threat Diagram shown below.

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 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:

• %User Profile%\Application Data\KB{Random Numbers}.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\E6D62C1B

(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 injects threads into the following normal process(es):

• Explorer.exe

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 Numbers}.exe" = "%User Profile%\Application Data\KB{Random Numbers}.exe"

Other System Modifications

This worm adds the following registry entries as part of its installation routine:

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

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows Media Center\4A5BC09B

HKEY_CURRENT_USER\Software\Microsoft\
Windows Media Center\E6D62C1B

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 File Name}.exe
shell\Open\Command={Malware File Name}.exe
shell\Open\Default=1
shell\Explore\Command={Malware File Name}.exe
shell\Autoplay\command={Malware File Name}.exe

Other Details

This worm deletes the initially executed copy of itself

NOTES:

This worm attempts to establish a connection to the following remote site:

• http://{Random URL}.ru:8080/rwx/B2_9w3/in/

Once a successfully connected, this worm may download its configuration file from its C&C server.

This worm uses a domain generation algorithm to generate random domains.