BKDR_ZEGOST.ECB

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 may be dropped by other malware.

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

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.

It may be dropped by the following malware:

• TROJ_DROPPER.ECB

Installation

This backdoor drops the following copies of itself into the affected system:

• %Program Files%\Common Files\Microsoft Shared\MSInfo\{random file name}.dll

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random file name}
ImagePath = "%System%\rundll32.exe "%Program Files%\Common Files\Microsoft Shared\MSInfo\{random file name}.dll",ServiceBoot"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random file name}
Start = "2"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random file name}
Type = "110"

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random file name}

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_{random file name}

Backdoor Routine

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

• Browse files
• Manage files
• Download and execute arbitrary files
• Execute shell commands
• Enumerate running processes
• Terminate processes
• Get drive information
• Log Keystrokes
• Logs the user off
• Copy clipboard data

Other Details

This backdoor drops the following file(s)/component(s):

• {All User's Profile}\{random file name}.dat
• %User Temp%\{random}_{random}.vbs - deleted after execution
• %Program Files%\Common Files\Microsoft Shared\MSInfo\{random file name}.ini - configuration file containing the location of BKDR_ZEGOST.ECB and TROJ_DROPPER.ECB

(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.. %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

NOTES:

This backdoor connects to the following command-and-control (C&C) server to send and receive commands:

• {BLOCKED}l.{BLOCKED}ews.com