System changes

The following system changes may indicate the presence of this malware:

• The presence of the following files:
  
  <system folder>\<six characters>.exe
  <system folder>\<six characters>.dll
  <system folder>\gei<random number>.dll
  %ProgramFiles%\<six characters>.exe
  %ProgramFiles%\<six characters>.dll
  %TEMP%\SOFTWARE.LOG
  %TEMP%\stf<five characters>.exe
  %windir%\<six characters>.exe
  %windir%\<six characters>.dll
   
• The presence of the file "lpk.dll" in all folders on your computer that contain files with an .exe, .rar or .zip extension
• The presence of services with random characters in their name, for example:
  
  Nationalyta Instruments dDomain Service"
  Microsoft Windows Uqdatexla Service
  phqghumeay
  na5eon2saul
  oejuvpvabo

DDoS:Win32/Nitol are a family of trojans that perform DDoS (distributed denial of service) attacks, allow backdoor access and control, download and run files and perform a number of other malicious activities on your computer. 

Installation

When run, variants of DDoS:Win32/Nitol may create copies of themselves as an EXE or DLL file, with a randomly generated file name of six characters (for example, "faxjwe.exe"). The trojan will create the copy in one of the following folders:

• %ProgramFiles%
• <system folder>
• %windir%

Note: %ProgramFiles% refers to a variable location that is determined by the malware by querying the operating system. The default location for the SystemRoot folder for Windows 2000, XP, 2003, Vista and 7 is "C:\Program Files".

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, Vista, and 7 it is "C:\Windows\System32".

Note: %windir% refers to a variable location that is determined by the malware by querying the operating system. The default installation location for the Windows folder for Windows 2000 and NT is "C:\WinNT"; and for XP, Vista, and 7 it is "C:\Windows". 

for example:

• %ProgramFiles%\viffic.exe
• <system folder>\hyjzuk.exe
• <system folder>\riffic.exe
• %windir%\4_Ss.dll

Some variants of DDoS:Win32/Nitol may install the service as a legacy driver with the following registry modification:

In subkey: "HKLM\System\CurrentControlSet\Enum\Root\LEGACY_<SERVICE>\0000"
Sets value: "Class"
With data: "LegacyDriver"

Sets value: "Legacy"
With data: "0x00000001"

where <SERVICE> is the service name installed by the malware.

The service's name is usually created from a hardcoded string (such as "111111111", "MSUpdqte" or "Nationald") with random characters inserted in or added to the string, as in the following examples:

• fuwu111111111
• MSUpdqtezni
• Nationaljrqd

The service's display name is also created from hardcoded strings with random characters insterted in or added to the string, as in the following examples:

• "<random characters>222222222", for example "fuwu222222222"
• "Microsoft Windows Uqdate<random characters> Service", for example "Microsoft Windows Uqdatexla Service"
• "National<random characters> Instruments dDomain Service", for example "Nationalyta Instruments dDomain Service"

Other variants use a completely random name for the service, for example:

• na5eon2saul
• oejuvpvabo
• phqghumeay

Some variants of DDoS:Win32/Nitol will instead pass the trojan as a DLL through the ServiceDll parameter, by modifying the following registry entry:

In subkey: HKLM\System\CurrentControlSet\Services\<service name>\Parameters
Sets value: "ServiceDll"
With data: "<malware file>.dll"

for example:

In subkey: HKLM\System\CurrentControlSet\Services\6to4\Parameters
Sets value: "ServiceDll"
With data: "%windir%\4_Ss.dll"

Some variants may delete themselves from their initial location. Earlier variants use the command line "cmd.exe /c del <malware file> > nul", while later variants may rename themselves as "%TEMP%\SOFTWARE.LOG" and set themselves to be deleted when you restart your computer.

Payload

Allows backdoor access and control

All variants of DDoS:Win32/Nitol allow unauthorized access and control of your computer by connecting to a remote server every 300 milliseconds to wait for commands. Using this backdoor, an attacker can perform the following actions on your computer:

• Download and run files
• Restart your computer
• Shut down your computer
• Start Internet Explorer
• Uninstall the trojan (by releasing the mutex, deleting the service, and setting the installed file attributes to normal)
• Update the trojan
• Perform DDoS attacks

Some variants of the trojan may download the update file to the %TEMP% folder in the format of "<five random characters>.exe, for example "axyjg.exe".

Other variants may use the following formats:

• "stf<five random characters>.exe", for example "stfaxyjig.exe"
• "bpk<five random characters>cn.exe", for example "bpkjxvacn.exe"

Connects to remote server

All variants of DDoS:Win32/Nitol connect to a remote server to upload information about your computer, including:

• The version of the trojan installed on your computer
• Your computer's geographic location
• Your computer's name
• Your computer's processing (CPU) speed
• The amount of installed memory (RAM) on your computer
• Your operating system type and version

The trojan connects to the remote server using a TCP or UDP connection. In the wild, we have observed variants connecting to the following remote servers using a TCP connection:

• 120272.3322.org:7000
• cbr.gnway.net:1484
• closewait.wowip.kr:12
• dnf43.3322.org:9001
• fei9988.3322.org:8080
• fghziyi.chibizx.com:8889
• hkl144.3322.org:7044
• huyiai.3322.org:7000
• mild443164.3322.org:7777
• rq00605.cn:8080
• w424010817.3322.org:8000
• woainimqq.3322.org:7000
• ylm466.3322.org:7000
• ysok.3322.org:7000

Injects code

Some variants of DDoS:Win32/Nitol inject code into svchost.exe so as to communicate with the remote server. These variants also use code injection to hinder detection and removal.

Drops component files

Some of the later variants (such as DDoS:Win32/Nitol.B) are distributed as an executable package (EXE) that contains a DLL component file. When run, these variants drop the DLL component as "lpk.dll" (with the "HIDDEN", "SYSTEM" and "READONLY" file attributes set) into all folders on all local and removable drives on your computer that contain files with an .exe, .rar or .zip extension.

These DLL files are appended with a copy of the EXE, and are are modified to load the EXE copy when they are run. 

In Windows, "lpk.dll" is always loaded when support for East Asian languages is installed. Once loaded, the LpkInitialize export will be called, which in this case will run the code to load the malware.

Another copy of "lpk.dll" may also be created in the <system folder> as "gei<random number>.dll", for example "gei33.dll".

Additional information

Each variant of the trojan creates a mutex as an infection marker to prevent multiple instances running on your computer. The mutex name is identical to the service name created by the malware, such as in the following examples:

• fuwu111111111
• MSUpdqtezni
• na5eon2saul
• Nationaljrqd

Related encyclopedia entries

DDoS:Win32/Nitol.B

Analysis by Patrik Vicol

Take the following steps to help prevent infection on your computer:

• Enable a firewall on your computer.
• Get the latest computer updates for all your installed software.
• Use up-to-date antivirus software.
• Limit user privileges on the computer.
• Use caution when opening attachments and accepting file transfers.
• Use caution when clicking on links to webpages.
• Avoid downloading pirated software.
• Protect yourself against social engineering attacks.
• Use strong passwords.

Enable a firewall on your computer

Use a third-party firewall product or turn on the Microsoft Windows Internet Connection Firewall.

• How to turn on the Windows Firewall in Windows 7
• How to turn on the Windows Firewall in Windows Vista
• How to turn on the Windows firewall in Windows XP

Get the latest computer updates

Updates help protect your computer from viruses, worms, and other threats as they are discovered. It is important to install updates for all the software that is installed in your computer. These are usually available from vendor websites. Instructions on how to download the latest versions of some common software is available from the following:

• Microsoft Malware Protection Center - Updating Software

You can use the Automatic Updates feature in Windows to automatically download future Microsoft security updates while your computer is on and connected to the Internet.

• How to turn on Automatic Updates in Windows 7
• How to turn on Automatic Updates in Windows Vista
• How to turn on Automatic Updates in Windows XP

Use up-to-date antivirus software

Most antivirus software can detect and prevent infection by known malicious software. To help protect you from infection, you should always run antivirus software, such as Microsoft Security Essentials, that is updated with the latest signature files. For more information, see 'Consumer security software providers'.

Limit user privileges on the computer

Starting with Windows Vista and Windows 7, Microsoft introduced User Account Control (UAC), which, when enabled, allowed users to run with least user privileges. This scenario limits the possibility of attacks by malware and other threats that require administrative privileges to run.

You can configure UAC in your computer to meet your preferences:

• User Account Control in Windows 7
• User Account Control in Windows Vista
• Applying the Principle of Least Privilege in Windows XP
• More on User Account Control

Use caution when opening attachments and accepting file transfers

Exercise caution with email and attachments received from unknown sources, or received unexpectedly from known sources. Use extreme caution when accepting file transfers from known or unknown sources.

Use caution when clicking on links to webpages

Exercise caution with links to webpages that you receive from unknown sources, especially if the links are to a webpage that you are not familiar with, unsure of the destination of, or suspicious of. Malicious software may be installed in your computer simply by visiting a webpage with harmful content.

Avoid downloading pirated software

Threats may also be bundled with software and files that are available for download on various torrent sites. Downloading "cracked" or "pirated" software from these sites carries not only the risk of being infected with malware, but is also illegal. For more information, see 'The risks of obtaining and using pirated software'.

Protect yourself from social engineering attacks

While attackers may attempt to exploit vulnerabilities in hardware or software to compromise a computer, they also attempt to exploit vulnerabilities in human behavior to do the same. When an attacker attempts to take advantage of human behavior to persuade the affected user to perform an action of the attacker's choice, it is known as 'social engineering'. Essentially, social engineering is an attack against the human interface of the targeted computer.

Use strong passwords

Attackers may try to gain access to your Windows account by guessing your password. It is therefore important that you use a strong password – one that cannot be easily guessed by an attacker. A strong password is one that has at least eight characters, and combines letters, numbers, and symbols. For more information, see 'Create strong passwords'.

To detect and remove this threat and other malicious software that may be installed on your computer, run a full-system scan with an appropriate, up-to-date, security solution. The following Microsoft products detect and remove this threat:

• Microsoft Security Essentials  or, for Windows 8, Windows Defender
• Microsoft Safety Scanner