BKDR_COREBOT.A

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 creates folders where it drops its files.

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

It connects to certain websites to send and receive information. However, as of this writing, the said sites are inaccessible.

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 and executes them:

• %AppDataLocal%\Microsoft\{GUID 2}\{GUID}.exe

(Note: %AppDataLocal% is the Application Data folder found in Local Settings, where it is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It adds the following processes:

• svchost.exe
• dllhost.exe - watchdog

It creates the following folders:

• %AppDataLocal%\Microsoft\{GUID 1}
• %AppDataLocal%\Microsoft\{GUID 2}

(Note: %AppDataLocal% is the Application Data folder found in Local Settings, where it is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It injects codes into the following process(es):

• Created processes

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{GUID 3} = "%AppDataLocal%\Microsoft\{GUID 2}\{GUID}.exe"

Backdoor Routine

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

• Download and Execute file
• Load and unload downloaded plugin
• Start and Stop plugin
• Perform Remote Shell
• Update URL list
• Update itself
• Update Plugin
• Modify Config
• Manage File
• Manage MBR
• Send gathered data

Information Theft

This backdoor gathers the following data:

• List Infected Processes
• Malware Information
• Plugin Information
• Victim Machine Information

Stolen Information

The stolen information is saved in the following file:

• {Created Folder}\{random file name}.dmp

Other Details

This backdoor connects to the following website to send and receive information:

• http://{BLOCKED}zo-sorelli.com/client
• http://{BLOCKED}mhyfuhg.ddns.net/verify
• http://{DGA}.{BLOCKED}s.net/verify

However, as of this writing, the said sites are inaccessible.