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Win32/Dursg


Win32/Dursg is a family of trojans that install malicious components as Firefox or Opera components. They redirect Internet search queries to malicious URLs that display advertisements or serve other malware.



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:

For more information on antivirus software, see http://www.microsoft.com/windows/antivirus-partners/.

Threat behavior

Win32/Dursg is a family of trojans that install malicious components as Firefox or Opera components. They redirect Internet search queries to malicious URLs that display advertisements or serve other malware.

Installation

Win32/Dursg may be distributed my other malware such as members of the Win32/Sality, Win32/Virut, Win32/Polip, Win32/Alureon, and Win32/Tracur families.

It creates the mutex "SERPv2" to ensure that only one instance of itslef is running in the computer at any given time.

Win32/Dursg drops a copy of itself using any of the following file names:

  • %APPDATA%\syswin\lsass.exe
  • %APPDATA%\systemproc\lsass.exe
  • %APPDATA%\system\lsass.exe

It may also drop a copy of itself as any of the following:

  • %APPDATA%\Microsoft\Windows\lsass.exe
  • %temp%\<random file name>.exe

If the currently-logged in user has administrator privileges on the computer, Win32/Dursg creates any of the following registry entries to ensure that its copy automatically runs at each Windows start:

In subkey: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
Sets value: "RTHDBPL"
With data: "<malware path and file name>"

In subkey: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
Sets value: "Lsass Service"
With data: "<malware path and file name>"

If the currently-logged in user does not have administrator privileges on the computer, Win32/Dursg creates any of the following registry entries to ensure that its copy automatically runs at each Windows start:

In subkey: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
Sets value: "Lsass Service"
With data: "<malware path and file name>"

In subkey: HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
Sets value: "Lsass Service"
With data: "<malware path and file name>"

It may also create the following registry modification as part of its installation process:

In subkey: HKCU\Identities
Sets value: "KillSelf"
With data: "ok"

Payload

Installs other malware
If the currently logged-in user has administrator privileges on the computer, Win32/Dursg installs a malicious Mozilla Firefox browser extension by dropping any of the following sets of files:

  • %ProgramFiles%\Mozilla Firefox\Extensions\<CLSID value>\install.rdf
  • %ProgramFiles%\Mozilla Firefox\Extensions\<CLSID value>\chrome.manifest
  • %ProgramFiles%\Mozilla Firefox\Extensions\<CLSID value>\chrome\content\timer.xul - detected as Trojan:Win32/Dursg
  • %appdata%\ Mozilla Firefox\Extensions\<CLSID value>\install.rdf
  • %appdata%\ Mozilla Firefox\Extensions\<CLSID value>\chrome.manifest
  • %appdata%\ Mozilla Firefox\Extensions\<CLSID value>\chrome\content\timer.xul - detected as Trojan:JS/Dursg

where <CLSID value> can vary depending on the sample. In the wild, we have seen the following <CLSID values> being used:

  • {8ce11043-9a15-4207-a565-0c94c42d590d}
  • {9ce11043-9a15-4207-a565-0c94c42d590d}

It may also install malicious Opera browser extensions as the following:

  • %appdata%\Opera\Opera\profile\user.js - detected as Trojan:JS/Dursg
  • %appdata%\Opera\Opera\profile\opera6.ini - configuration file pointing to the "user.js" file

Redirects web searches
Win32/Dursg monitors the user's web browsing if and may redirect web searches to a malicious URL when one of the following search engines are used:

  • Google
  • Yahoo
  • AOL
  • Ask
  • Bing

Some variants may also affect the following search engines and domains:

  • Yandsearch
  • Bigmir
  • Aport
  • Mail.ur

Win32/Dursg only monitors web searches if Firefox or Opera is used for the searches.

In the wild, this Trojan has been observed to redirect searches to the following domains:

  • avabon.com
  • gewebsearch.com
  • clickedtraff.com
  • macsonq.com
  • clickstraffic.net
  • iwantbeborin.com

Analysis by Rodel Finones


Symptoms

System changes

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

  • The presence of the following files:
    • %APPDATA%\syswin\lsass.exe
    • %APPDATA%\systemproc\lsass.exe
    • %APPDATA%\system\lsass.exe
  • The presence of the following registry modifications:
    In subkey: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
    Sets value: "RTHDBPL"
    In subkey: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
    Sets value: "Lsass Service"
    In subkey: HKCU\Identities
    Sets value: "KillSelf"
    With data: "ok"

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 http://www.microsoft.com/windows/antivirus-partners/.

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. 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 eight characters, and combines letters, numbers, and symbols. For more information, see http://www.microsoft.com/protect/yourself/password/create.mspx.


Alert level: Severe
This entry was first published on: Jul 11, 2011
This entry was updated on: Jul 11, 2011

This threat is also detected as:
No known aliases