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Win32/Parite


Win32/Parite is a family of polymorphic file infectors that targets computers running Microsoft Windows. The virus infects .exe and .scr executable files on the local file system and on writeable network shares. In turn, the infected executable files perform operations that cause other .exe and .scr files to become infected.


What to do now

It is not possible to recover manually from Win32/Parite. Consult your antivirus software vendor for specific directions for removing this Trojan.

Threat behavior

Win32/Parite is a packed, encrypted virus that infects files on the local file system and on writeable network shares. The virus repeatedly performs a sequence whereby it selects an .exe or .scr executable file, infects the file, waits a random time interval, selects and infects another file, and so on.
 
To each file that it selects for infection, the virus appends a new code section named ".<three random alphabetic characters>", such as .mpg. The virus changes the code-entry point of the file to the new, appended section. The virus contains certain code that it unpacks, re-encrypts, re-packs, and then copies to the new section of the executable file. This copied code consists of certain DLL code and some additional execution instructions.
 
When a file infected in this way runs, the execution instructions in the appended section of the file unpack and decrypt the DLL code in the appended section and drop it as a new file into the Windows temporary directory. The name of the dropped DLL consists of 4 randomly-chosen alphanumeric characters: the first three characters are alphabetic and the final character is a digit. Although the file is actually a DLL, the file extension is .tmp. So for example, the file could have a name like fia1.tmp.
 
The virus may also creates a marker in the registry:
Adds value: PINF
To subkey: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer
This value contains the full path to the dropped DLL. Win32/Parite may check for this registry entry to determine whether the virus is already running on the computer.
 
The execution instructions in the appended section of the infected file load the dropped DLL. The DLL exports a start function which contains the main virus code. The virus code calls the start function, which injects the DLL into the explorer.exe process. When a certain condition is satisfied, the DLL code runs and infects other .exe and .scr executable files.
 
Win32/Parite does not run executable files that it infects. When an infected file runs (for example, when a user or the system runs the file), the virus code in the appended section runs and then returns control to the original code-entry point of the executable file. The executable file then runs normally even though it is infected, so there may be no readily apparent indication to a user of any malicious activity.

Symptoms

The following registry modification may be a result of infection by Win32/Parite:
  • Presence of value: PINF
    in subkey: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer

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 Web pages.
  • 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 Web sites.
 
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 http://www.microsoft.com/security/antivirus/av.aspx.
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 e-mail 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 Web pages
Exercise caution with links to Web pages that you receive from unknown sources, especially if the links are to a Web page 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 Web page 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. For more information, see 'What is social engineering?'.
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 8 characters, and combines letters, numbers, and symbols. For more information, see http://www.microsoft.com/protect/yourself/password/create.mspx.

Alert level: High
This entry was first published on: Nov 30, 2004
This entry was updated on: Jun 01, 2010

This threat is also detected as:
  • W32/Pinfi (Symantec)
  • W32/Pate (McAfee)
  • PE_PARITE (Trend Micro)
  • Win32.Parite (Kaspersky)