TROJ_KILLMBR.DS

This malware is involved in the Master Boot Record (MBR) wiper outbreak that targeted users in South Korea during March of 2013. It drops and executes malware on affected systems, including a destructive payload that wipes the affected system's MBR. Users affected by this malware may find their systems freezing, shutting down, and unable to run.

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

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Arrival Details

This Trojan 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 Trojan drops the following component file(s):

• %User Temp%\alg.exe - PuTTY client
• %User Temp%\conime.exe - PuTTY client
• %User Temp%\~pr1.tmp - detected by Trend Micro as UNIX_KILLMBR.A

(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 and executes the following files:

• %User Temp%\AgentBase.exe - detected by Trend Micro as TROJ_KILLMBR.SM

(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.)

NOTES:

This Trojan searches the system for the configuration files of two SSH clients:

• Felix Deimel's mRemote: %AppDataLocal%\Felix_Deimel\mRemote\confCons.xml
• VanDyke's Secure CRT: %Application Data%\VanDyke\Config\Sessions

If a configuration file is found, it parses it and looks for a user with root privileges on a remote system and extracts connection information.

Using the connection information, it connects to the remote system using the dropped Putty clients. Once connection has been established, it uploads and execute the file %User Temp%\~pr1.tmp as /tmp/cups on the remote system.