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.
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:
- <system folder>
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".
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:
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:
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"
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.
Note: %TEMP% refers to a variable location that is determined by the malware by querying the operating system. The default location for the All Users Profile folder for Windows 2000
, and 2003
". For Windows Vista
, the default location is "C:\Users
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:
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".
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:
Related encyclopedia entries
Analysis by Patrik Vicol