BKDR_AFCORE.DI

This backdoor monitors the browsing activities of the user and logs keystroke when the user is accessing sites with certain strings.

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 injected into processes running in memory.

It opens a random port to allow a remote user to connect to the affected system. Once a successful connection is established, the remote user executes commands on the affected system.

It requires its main component to successfully perform its intended routine.

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 non-malicious files:

• %System%\{random filename 1}.dat
• %System%\{random filename 2}.dat
• %System%\{random filename 3}.dat
• %System%\{random filename 4}.dat
• %Current%\{malware filename}.dat

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

It drops the following copies of itself into the affected system:

• %System%\{random filename 1}.ocx

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

It may be injected into processes running in memory.

Autostart Technique

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

HKEY_CLASSES_ROOT\CLSID\{random CLSID}\
InprocServer32
(default} = {malware path and filename}

HKEY_CLASSES_ROOT\CLSID\{random CLSID}\
InprocServer32
(default) = %System%\{random filename 1}.ocx

Other System Modifications

This backdoor adds the following registry keys as part of its installation routine:

HKEY_CLASSES_ROOT\CLSID\{random CLSID}

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
ShellIconOverlayIdentifiers\{malware filename}

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
ShellIconOverlayIdentifiers\{random filename 1}

Backdoor Routine

This backdoor opens a random port to allow a remote user to connect to the affected system. Once a successful connection is established, the remote user executes commands on the affected system.

Other Details

This backdoor requires its main component to successfully perform its intended routine.

NOTES:

It may perform the following actions:

• Create, list, and delete cookies
• Flood drives
• Get IPC, log, and hook timeouts
• Manipulate files
• Obtain various system information (i.e., local time, drive information, idle time)
• Perform distributed denial of service (DDoS) attack against a target site
• Resolve host names
• Respawn or uninstall itself
• Restart Windows
• Turn off the system

It monitors the following applications:

• explorer.exe
• iexplore.exe
• firefox.exe
• opera.exe
• skype.exe

It also monitors the browsing activities of the user and logs keystroke when the user is accessing sites with the following strings:

• *.nhs.net/*
• *.nhs.uk/*
• *.hilton.*
• *.yahoo.*
• *.google.*