BKDR_NECURS.BGSJ

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 dropped by other malware.

It executes then deletes itself afterward. It is injected into all running processes to remain memory resident.

It modifies registry entries to disable the Windows Firewall settings. This action allows this malware to perform its routines without being deteted by the Windows Firewall.

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

It creates an event.

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.

It may be dropped by the following malware:

• TSPY_FAREIT.VAOV

Installation

This backdoor drops the following file(s)/component(s):

• %System%\drivers\{random file name}.sys - detected as RTKT_NECURS.B

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

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

• %Windows%\Installer\{GUID}\syshost.exe

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

It creates the following folders:

• %Windows%\Installer\{GUID}

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

It executes then deletes itself afterward.

It is injected into all running processes to remain memory resident.

Autostart Technique

This backdoor registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\syshost32
ImagePath = ""%Windows%\Installer\{GUID}\syshost.exe" /service"

It creates the following registry entries to enable automatic execution of dropped component at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
syshost32 = "%Windows%\Installer\{GUID}\syshost.exe"

It registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\syshost32

It registers its dropped component as a system service to ensure its automatic execution at every system startup. It does this by creating the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random file name}

Other System Modifications

This backdoor modifies the following registry entries to disable the Windows Firewall settings:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\DomainProfile
DoNotAllowExceptions = "0"

(Note: The default value data of the said registry entry is "1".)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile
DoNotAllowExceptions = "0"

(Note: The default value data of the said registry entry is "1".)

Backdoor Routine

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

• http://{BLOCKED}.{BLOCKED}.81.244
• http://{BLOCKED}.{BLOCKED}.56.54
• http://{BLOCKED}.{BLOCKED}.31.41

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

Other Details

This backdoor connects to the following URL(s) to check for an Internet connection:

• facebook.com
• microsoft.com

It creates the following event(s):

• Global\NitrGB
• Local\NitrGB

NOTES:

This backdoor performs a NETSH.EXE command that disable Windows Firewall depending on the operating system version.

It connects to the following time servers to synchronize time:

• {number}.pool.ntp.org