BKDR_SERKDES.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 does not have any propagation routine.

It executes commands from a remote malicious user, effectively compromising the affected system. However, as of this writing, the said sites are inaccessible.

It deletes the initially executed copy of itself.

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:

• %User Temp%/Del{random number}.tmp
• %System%\rasaut.dll

(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.. %System% is the Windows system folder, which is usually C:\Windows\System32.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\ResAuto\Parameters
ServiceDll = "%System%\rasaut.dll"

(Note: The default value data of the said registry entry is %System%\rasauto.dll.)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\RasAuto
Start = "2"

(Note: The default value data of the said registry entry is 3.)

Other System Modifications

This backdoor modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\RasAuto
DisplayName = "Remote Access Auto Connection Manager" (Windows Vista and higher versions)

(Note: The default value data of the said registry entry is @%Systemroot%\system32\rasauto.dll,-200.)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\RasAuto
Type = "288"

(Note: The default value data of the said registry entry is 32.)

Propagation

This backdoor does not have any propagation routine.

Backdoor Routine

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

• Download file
• Execute file
• Delay process
• Send system information such as host name and IP

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

• paqsr.{BLOCKED}s.de:443
• {BLOCKED}.2.9:443

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

Other Details

This backdoor deletes the initially executed copy of itself

NOTES:

It does not have rootkit capabilities.

It does not exploit any vulnerability.