BKDR_HELOAG.SM

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 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.

Installation

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

• %Windows%\ThunderUpdate.exe

(Note: %Windows% is the Windows folder, which is usually C:\Windows.)

Autostart Technique

This backdoor modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "Explorer.exe %Windows%\ThunderUpdate.exe"

(Note: The default value data of the said registry entry is Explorer.exe.)

Backdoor Routine

This backdoor opens the following port(s) where it listens for remote commands:

• 8090

It executes the following commands from a remote malicious user:

• Download files and save in the Temporary Folder
• Delete files
• Execute files
• Create threads for received commands
• Terminate threads
• Insert malicious script tags into Web pages
• Get computer name

It connects to the following URL(s) to send and receive commands from a remote malicious user:

• cncln.{BLOCKED}.ln.cn
• {BLOCKED}.{BLOCKED}.130.247

NOTES:

This backdoor creates a thread that continuously receives IP addresses from the from a host botnet. It then creates a thread for each IP address received and waits for remote commands.