Encyclopedia entry
Updated:
Apr 17, 2011
| Published:
Jul 30, 2007
Aliases
Win32/Virut
(CA)
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Virus.Win32.Virut
(Kaspersky)
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W32/Virut
(Norman)
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W32/Virut
(Sophos)
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W32/Virut
(McAfee)
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W32.Virut
(Symantec)
Alert Level
(?)
Severe
Antimalware protection details
Microsoft recommends that you download the
latest definitions
to get protected.
Summary
Win32/Virut is a family of file infecting viruses that target and infect .EXE and .SCR files accessed on infected systems. Win32/Virut also opens a backdoor by connecting to an IRC server, allowing a remote attacker to download and run files on the infected computer.
Symptoms
The following symptoms may be indicative of a Virus:Win32/Virut infection:
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Network traffic on TCP port 65520 with connection to IRC server proxima.ircgalaxy.pl, on channel &virtu
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Increase in file size of infected files
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Infected files fail during execution and have a recent modified date property
Technical Information (Analysis)
Win32/Virut is a family of file infecting viruses that target and infect .EXE and .SCR files accessed on infected systems. Win32/Virut also opens a backdoor by connecting to an IRC server, allowing a remote attacker to download and run files on the infected computer.
Installation
Win32/Virut creates a mutex named VT_3 which it uses to prevent multiple copies of itself from running on the host system. Win32/Virut disables Windows System File Protection (SFP) by injecting code into WINLOGON.EXE. The injected code patches sfc_os.dll in memory which in turn allows the virus to infect files protected by SFP.
Win32/Virut injects code into other processes and this code will infect files with extensions .EXE and .SCR accessed by those processes. Win32/Virut avoids infecting files whose names contain any of the following:
Win32/Virut opens a connection with Internet Relay Channel (IRC) servers as follows:
Server: proxima.ircgalaxy.pl
Port: 65520
Channel: &virtu
This IRC connection allows a remote attacker to control the infected machine and force it to download and execute potentially unwanted software or malware.
Prevention
Take the following steps to help prevent infection on your computer:
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Enable a firewall on your computer.
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Get the latest computer updates for all your installed software.
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Use up-to-date antivirus software.
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Limit user privileges on the computer.
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Use caution when opening attachments and accepting file transfers.
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Use caution when clicking on links to Web pages.
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Avoid downloading pirated software.
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Protect yourself against social engineering attacks.
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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
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.
Recovery
Note: The method of infection used by Win32/Virut can damage some infected files beyond repair. In these cases, in order to return a machine to its pre-infected state, it may be necessary to install a clean backup of the operating system and associated applications.
Recovering from recurring infections on a network
The following additional steps may need to be taken to completely remove this threat from an infected network, and to stop infections from recurring from this and other similar types of network-spreading malware:
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Ensure that an antivirus product is installed on ALL machines connected to the network that can access or host shares (see above for further detail).
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Ensure that all available network shares are scanned with an up-to-date antivirus product.
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Remove any unnecessary network shares or mapped drives.
Note: Additionally it may be necessary to temporarily change the permission on network shares to read-only until the disinfection process is complete.
