BKDR_LAYRUI.A

This backdoor deletes autostart registry entries associated with the processes it terminates to completely disable applications.

It may also connect to Internet Relay Chat (IRC) servers and receive commands from a remote user.

It deletes the file(s) associated with the process(es) it terminates. It does the said routine to completely disable programs and applications.

Installation

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

• %Windows%\system32\svihost.exe

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Windows Updates = "%Windows%\system32\svihost.exe"

Other System Modifications

This backdoor deletes the following files:

• %Windows%\system32\update.exe
• %Windows%\system32\server.txt
• %Windows%\server.txt
• %Windows%\system32\check.txt

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

It adds the following registry entries as part of its installation routine:

HKEY_CURRENT_USER\Software\Policies\
Microsoft\Internet Explorer\Control Panel
Homepage = 0

HKEY_LOCAL_MACHINE\Software\Policies\
Microsoft\Internet Explorer\Control Panel
Homepage = 0

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableTaskMgr = 0

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableRegistryTools = 0

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableTaskMgr = 0

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableRegistryTools = 0

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Internet Explorer\Main
Start Page = "http://autokiemthe.com"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Main
Start Page = "http://autokiemthe.com"

It deletes autostart registry entries associated with the processes it terminates to completely disable applications.

It deletes the following registry keys:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Windows Updates =

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Windows Update =

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Windows Update =

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Windows Updates =

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Internet Explorer\Main
Window Title =

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Main
Window Title =

Backdoor Routine

This backdoor may also connect to Internet Relay Chat (IRC) servers and receive commands from a remote user.

It accesses a remote Internet Relay Chat (IRC) server where it receives the following commands from a remote malicious user:

• Quit – wait for another backdoor command
• Exit – closes the TCP connection
• logout – asks the remote malicious user to logout. This will disable all backdoor commands.
• run – executes a file that is not visible to the user
• check – checks if specified process is running
• master – display connected user and channel
• login - asks the remote malicious user to login. Correct password enables all backdoor commands. cmd - open a remote shell
• Download - downloads a file
• Update - same function as Download
• rundos - execute dos command
• abort - stops current download
• pl - lists all running processes
• openhost - setups ftp
• chupinh - Screen capture then send file to remote malicious user via ftp
• Getfile - uploads file in ftp
• cp - close process
• ddos - download and execute file "%Windows%\system32\ddosw.exe"
• stop - uninstall "%Windows%\system32\ddosw.exe" from the system
• Visit - access a website using Internet Explorer
• shutdown - shuts down the system
• reboot - reboots the system
• Del - delete a file
• Copy - copy a file
• Move - move a file
• info - lists system information of the user (e.g. OS Version, Computer Name, UserName, IP Address) Chat - enables chat
• Ver - displays the malware version
• Help - lists all backdoor commands

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

Process Termination

This backdoor terminates the following processes if found running in the affected system's memory:

• FastHelper.exe
• bdss.exe
• svchosts.exe
• svhost.exe
• svhcost.exe
• svchos.exe
• at4kt.exe
• Hackchucphuc.exe
• Bkav2006.exe
• Wupdate.exe
• EtherD.exe

It terminates the following malware-related processes:

• svihost.exe
• Dangkysudung.exe

It deletes the file(s) associated with the process(es) it terminates. It does the said routine to completely disable programs and applications.

Download Routine

This backdoor downloads an updated copy of itself from the following website(s):

• http://{BLOCKED}viet.com/alo/svihost.exe
• http://{BLOCKED}ip.com/alo/update.exe

It connects to the following URL(s) to download its configuration file:

• http://{BLOCKED}viet.com/bot1/dunghoitaisao.php
• http://{BLOCKED}ip.com/alo/dunghoitaisao.php

It saves the files it downloads using the following names:

• %Windows%\system32\check.txt
• %Windows%\system32\update.exe

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

Other Details

This backdoor closes application windows that contain the following strings in the title bar:

• EtherDetect Packet Sniffer

It sets the attributes of the following file(s) to Hidden and System:

• %Windows%\system32\svihost.exe

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

NOTES:

This backdoor removes the following processes from being displayed in Windows Task Manager:

• svihost.exe
• Dangkysudung.exe