Worm:Win32/Nuqel.AN

Worm:Win32/Nuqel.AN is a member of Win32/Nuqel - a family of worms that may spread via removable or network drives and particular messenger applications. It may also modify a number of system settings to faciliate its actions on an affected computer, and contact a remote host.

When executed, Worm:Win32/Nuqel.AN copies itself to the following locations:
%windir%\hinhem.scr
%windir%\scvshosts.exe
<system folder>\blastclnnn.exe
<system folder>\scvshosts.exe

 

Note - <system folder> refers to a variable location that is determined by the malware by querying the Operating System. The default installation location for the System folder for Windows 2000 and NT is C:\Winnt\System32; and for XP and Vista is C:\Windows\System32.

 

The malware modifies the following registry entry/ies to ensure that its copy executes at each Windows start:

Adds value: "Yahoo Messengger"
With data: "c:\windows\system32\scvshosts.exe"
To subkey: HKCU\SOFTWARE\Microsoft\windows\currentversion\run

 

Adds value: "Shell"
With data: "explorer.exe scvshosts.exe"
To subkey: HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon

 

The malware drops the following file(s) to an affected machine:

 

The malware attempts to create a scheduled Windows task that runs the worm at 9:00 am every day of the week, by running the following Windows shell command instruction:
cmd.exe /C AT /delete /yes
cmd.exe /C AT 09:00 /interactive /EVERY:m,t,w,th,f,s,su <system folder>\blastclnnn.exe

Variants of the Win32/Nuqel family may use a number of different methods in order to spread to other computers.
MSN Messenger
Win32/Nuqel may spread using a number of different messaging applications, including Yahoo Messenger, AIM, Windows Messenger and Google Talk. It sends a message to all of the infected user's contacts with a link to a copy of itself.

Network shares
Some variants of Win32/Nuqel also try to spread through network shares by querying the following registry entry and copying themselves to any shared folders specified by this entry: HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\WorkgroupCrawler\Shares

 

Removable drives

Worm:Win32/Nuqel.AN copies itself to the following location/s on removable drives:
<targeted drive>:\new folder.exe
<targeted drive>:\scvshosts.exe
<targeted drive>:\subst.exe.

It also places an autorun.inf file in the root directory of the targeted drive. Such autorun.inf files contain execution instructions for the operating system, so that when the removable is accessed from another machine supporting the Autorun feature, the malware is launched automatically.

Note: this worm was observed to write an executable and create an autorun.inf file on a targeted drive in our automated testing environment. This is particularly common malware behaviour, generally utilized in order to spread malware from machine to machine.

It should also be noted that autorun.inf files on their own are not necessarily a sign of infection, as they are used by legitimate programs and installation CDs.

Terminates processes

Worm:Win32/Nuqel.AN terminates the following processes should they be running on an affected machine:

cmd.exe

 

Modifies system settings

The malware modifies the affected computer system's settings by making the following changes to the registry:

Sets value: "DisableTaskMgr"
With data: "1"
To subkey: HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System

This modification disables the system utility Task Manager.

 

Contacts remote hosts

The malware may contact the following remote hosts using port 80:

setting3.9999mb.com
setting3.yeahost.com
www.freewebs.com

Commonly, malware may contact a remote host for the following purposes:

• To confirm Internet connectivity
• To report a new infection to its author
• To receive configuration or other data
• To download and execute arbitrary files (including updates or additional malware)
• To receive instruction from a remote attacker
• To upload data taken from the affected computer