TROJ_NECURS.TENI

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

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.

It creates an event. It deletes the initially executed copy of itself.

Arrival Details

This Trojan 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 Trojan drops the following component file(s):

• %System%\drivers\{random}.sys - detected as RTKT_NECURS.AH

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

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

• %Application Data%\{GUID}\syshost.exe - if not logged in as an Administrator
• %Windows%\Installer\{GUID}\syshost.exe - if logged in as an Administrator

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.. %Windows% is the Windows folder, which is usually C:\Windows.)

It creates the following folders:

• %Windows%\Installer\{GUID} - if logged in as an Administrator
• %Application Data%\{GUID} - if not logged in as an Administrator

(Note: %Windows% is the Windows folder, which is usually C:\Windows.. %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)

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

Autostart Technique

This Trojan 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 adds the following registry entries to enable its automatic execution 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 keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random}

Other System Modifications

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAcces\Parameters\
FirewallPolicy\DomainProfile
EnableFirewall = "0"

Other Details

This Trojan 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

It deletes the initially executed copy of itself

NOTES:

It performs a netsh.exe command that disables Windows Firewall depending on the OS version. It elevates certain privileges when not in Administrator mode.

It connects to the following site to send and receive data:

• http://{BLOCKED}.{BLOCKED}8.90.136/news/index.php

The received data is written to a file in the %User Temp% folder.

However, as of this writing, no data was received from the server.