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Virus:Win32/Xpaj


Virus:Win32/Xpaj is a family of viruses that spread by infecting local files and removable and network drives. The virus attempts to download arbitrary files which may be detected as other trojans.

The virus is capable of infecting executable (EXE), driver (DLL), screen saver (SCR) and system (SYS) files.

In the wild, we have observed this virus distributed via file sharing sites, masquerading as a key generator. It may also arrive on your computer via a drive-by download.



What to do now

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:

Additional remediation steps for Virus:Win32/Xpaj

Virus:Win32/Xpaj may make lasting changes to infected files that will not be restored by detecting and removing this threat. To return an infected computer to its pre-infected state, files infected by Virus:Win32/Xpaj must be restored from backup.

Threat behavior

Installation

You may inadvertently download and run Virus:Win32/Xpaj, thinking it is a certain program such as a key generator.

In the wild, we have observed the virus using the following icon to make itself appear as a program:

It may also arrive on your computer via a drive-by download.

When run, the virus infects files on your computer and on removable and network drives.

When those files are opened (either by yourself or during the normal operation of your computer), the virus code is run again and infects yet more files, thus ensuring the virus is continuously running and infecting files.

Spreads via…

File infection

Virus:Win32/Xpaj targets files in the <system folder> and %ProgramFiles% folders and their subfolders. It creates a list of all files with the following extensions and randomly chooses files to infect from that list:

  • .exe
  • .dll
  • .scr
  • .sys

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, 7, and 8 it is "C:\Windows\System32".

Note: %ProgramFiles% refers to a variable location that is determined by the malware by querying the operating system. The default location for the Program Files folder for Windows 2000, XP, 2003, Vista, 7, and 8 is "C:\Program Files".
 
Virus:Win32/Xpaj copies a chosen file to the %TEMP% folder with a temporary file name (for example, "%TEMP%/<hexadecimal value>.tmp"). The virus infects this copy of the file, and then overwrites the original file with the infected copy.

During the process of file infection, the virus deletes the temporary file; therefore, no clean copies of the original files remain in %TEMP%.

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, XP, and 2003 is "C:\DOCUME~1\<user>\LOCALS~1\Temp". For Windows Vista, 7 and 8, the default location is "C:\Users\<user name>\AppData\Local\Temp".

Virus:Win32/Xpaj does not infect protected Windows files. 

Removable and network drives

Virus:Win32/Xpaj infects files in removable and network drives, using the same method as it uses for infecting local files.

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

This is particularly common malware behavior, generally used in order to spread malware from computer to computer.

It should 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 media.

Payload

Downloads arbitrary files

Virus:Win32/Xpaj  connects to a remote server to report infection and receive instructions, including the command to download arbitrary files which may be detected as other malware. This malware may be related to online "click-fraud" where your Internet browser is redirected to malicious URLs.

At the time of analysis, the servers the virus attempts to connect to were not available. Therefore, we are unable to verify the files the virus downloads.

The server the virus connects to is hardcoded in the virus's code, we have observed the virus attempting to connect to "74.72.<removed>.125" ("nortiniolosto.com").

If it cannot connect to the remote server, it will generate URLs and attempt to connect to them, for example:

  • adtdqpucl.com
  • adu.com
  • aebvf.com
  • ajfvbjkmpl.com
  • fuijuxgvcvo.com
  • rswsqq.com

The virus downloads the arbitrary files to the %windir% directory with a random file name, for example "rafm.fph".

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, 7, and 8 it is "C:\Windows".

Infects the master boot record

Some variants of Virus:Win32/Xpaj infect the MBR (master boot record) with their own malicious copy in an attempt to hinder detection and removal of the virus. The malicious MBR is detected as Trojan:DOS/Xpaj.A and Trojan:DOS/Xpaj.B.

Modifying the MBR allows the virus to load before Windows, thus giving it greater control over your system.

Additional information

The virus initially creates a file in the %windir% directory with a file name in the format <random letters>.<random letters>, for example "sqna.oci".

The virus uses this file as an infection marker.

Related encyclopedia entries

Trojan:DOS/Xpaj.A

Trojan:DOS/Xpaj.B

Analysis by Rodel Finones


Symptoms

There are no common symptoms associated with this threat. Alert notifications from installed antivirus software may be the only symptoms.

Prevention

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.

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:

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.

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:

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'.


Alert level: Severe
This entry was first published on: Nov 29, 2011
This entry was updated on: Jan 09, 2013

This threat is also detected as:
  • Win32/Goblin.D.Gen (ESET)
  • Win32/Goblin.E.Gen (ESET)
  • Virus.Win32.Xpaj.gen (Kaspersky)
  • Virus.Win32.Xpaj.genb (Kaspersky)
  • Virus.Win32.Xpaj.genc (Kaspersky)
  • W32.Xpaj.B (McAfee)
  • Virus.Win32.Xpaj (Ikarus)
  • PE_XPAJ.C (Trend Micro)
  • Mal/Xpaj-B (Sophos)