BKDR_THOPER.AB

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 executes then deletes itself afterward.

It does not have any propagation routine.

It executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

It does not have any downloading capability.

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 and executes the following files:

• %All Users Profile%\Application Data\mspool.DLL - also detected as BKDR_THOPER.AB

(Note: %All Users Profile% is the All Users or Common profile folder, which is C:\Documents and Settings\All Users in Windows 2000, XP, and Server 2003, and C:\ProgramData in Windows Vista and 7.)

It drops the following non-malicious file:

• %User Temp%\3.doc

(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 executes then deletes itself afterward.

Autostart Technique

This backdoor registers its dropped component as a system service to ensure its automatic execution at every system startup. It does this by creating the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\mspool

Propagation

This backdoor does not have any propagation routine.

Backdoor Routine

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

• File Manipulation
• Registry Management
• Service Management
• Process Management
• Get System Information (Disk Information, OS Version, Computer Name, Drive Information, Volume Information, Network Information)
• Retrieve cache passwords
• Perform shell command
• Donwload and execute arbitrary file
• Microsoft Database Query
• Remote desktop connection
• Shutdown, Restart and Lock Workstation
• Display a message box
• Manage Application Windows
• Log keystrokes
• Capture screenshots

It connects to the following websites to send and receive information:

• {BLOCKED}m.{BLOCKED}-show.org:443

Download Routine

This backdoor does not have any downloading capability.

Other Details

This backdoor connects to the following URL(s) to check for an Internet connection:

• download.windowsupdate.com

NOTES:

It does not have rootkit capabilities.

It does not exploit any vulnerability.