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Malicious Software Encyclopedia: Win32/Alureon

Published: October 19, 2009

Win32/Alureon is a family of data-stealing trojans. These trojans allow an attacker to intercept incoming and outgoing Internet traffic in order to gather confidential information such as user names, passwords, and credit card data. The Win32/Alureon trojan may also allow an attacker to transmit malicious data to the infected computer. The trojan may modify DNS settings on the host computer to enable the attacker to perform these tasks. Therefore it may be necessary to reconfigure DNS settings after the trojan is removed from the computer.

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On This Page
Threat OverviewThreat Overview
Aliases (Also Known As)Aliases (Also Known As)
Technical AnalysisTechnical Analysis
How to Prevent InfectionHow to Prevent Infection
How to Tell If Your Computer Is InfectedHow to Tell If Your Computer Is Infected
How to Recover from InfectionHow to Recover from Infection

Threat Overview

Class/typeTrojan - Data Theft
DiscoveredSeptember 15, 2005
CirculatingYes
Child variantsTrojan:Win32/Alureon.A
Trojan:Win32/Alureon.B
Trojan:Win32/Alureon.E
TrojanDownloader:Win32/Alureon.A
Affected operating systems
Affected software Not specified
Infection ratingLow
Recovery difficultyModerate
Damage ratingMedium
Transmission ratingLow

Aliases (Also Known As)

Different antivirus vendors may be using different names to refer to this malicious software. Here are some of the names currently in use by antivirus software vendors participating in the Microsoft Virus Information Alliance (VIA):

  • CA: Win32/Alureon

    • Learn more about the Microsoft Virus Information Alliance.

    Technical Analysis

    Win32/Alureon is a family of data-stealing trojans. These trojans allow an attacker to intercept incoming and outgoing Internet traffic in order to gather confidential information such as user names, passwords, and credit card data. The Win32/Alureon trojan may also allow an attacker to transmit malicious data to the infected computer. The trojan may modify DNS settings on the host computer to enable the attacker to perform these tasks. As a result, it may be necessary to reconfigure DNS settings after Win32/Alureon is removed from the computer.
     
    Instances of the Win32/Alureon trojan may contain various malicious components. Following are three examples of Win32/Alureon components.
     
    One component of the Win32/Alureon family specifies the DNS servers to be used by the host computer. To do so, this component sets DNS server addresses for each network adapter on the host computer by modifying values in certain registry subkeys associated with the adapters. For example, the trojan component may:
    • Modify registry value: DhcpNameServer
      under subkey: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters
    • Modify registry values:
      NameServer
      DhcpNameServer
      under certain subkeys of subkey:
      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces
    The same component may also set the fields “IpDnsAddress” and “IpDns2Address” to specific DNS servers in the Windows dial-up configuration file that is for the All Users profile. The trojan sets these fields if the configuration file already contains data. The dial-up configuration file location for the All Users Profile for Windows XP/Server 2003/Vista is: %allusersprofile%\Application Data\Microsoft\Network\Connections\Pbk\rasphone.pbk
     
    To cause these new DNS settings to take immediate effect, the Win32/Alureon trojan runs the following commands:
    • ipconfig.exe /flushdns
      ipconfig.exe /registerdns
      ipconfig.exe /dnsflush
      ipconfig.exe /renew
      ipconfig.exe /renew_all
     
    A second Win32/Alureon component may perform the following operations:
    • Create a randomly named copy of itself under the Windows system folder.
      Note: By default, on Windows 95/98/ME the location of the Windows system folder is C:\Windows\System. On Windows NT/2000, the default location is C:\Winnt\System32. On Windows XP/Server 2003/Vista, the default location is C:\Windows\System32.
    • Inject threads into local processes to delete itself and perform other tasks.
    • Create registry entries under HKEY_CLASSES_ROOT.
    • Create registry subkeys such as: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\ruins
     
    A third Win32/Alureon component may perform the following operations:
    • Gather URLs from the user's Web-browsing history.
    • Create a new registry value in subkey
      HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion
      and place random data in that value.
    • Create a randomly named copy of itself under the Windows system folder
    • Modify the registry to cause the trojan copy to run automatically each time Windows starts:
    Adds value: <name of trojan copy>
    With data: <path to trojan copy>
    In subkey: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run 
    • Delete the following registry entries under subkey HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run:
      • The registry value whose name matches the name of the trojan file that is currently running.
      • The registry subkey whose name matches the name of the trojan file that is currently running.
    • Run Internet Explorer or the default Web browser and inject code into the corresponding new process. The injected code may take various actions, including changing DNS server settings on the host computer and downloading and running files from certain Web sites.
    • Run a new instance of explorer.exe and inject code into the corresponding new process. The injected code may take various actions, including deleting the Win32/Alureon file that is running.

    Some Win32/Alureon components may disable or clear the existing Internet Explorer proxy settings.

    How to Prevent Infection

    Take the following steps to help prevent infection on your system:
    • Enable a firewall on your computer.
    • Get the latest computer updates for all your installed software.
    • Use up-to-date antivirus software.
    • 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.
    To turn on the Windows Firewall in Windows Vista
    1. Click Start, and click Control Panel.
    2. Click Security.
    3. Click Turn Windows Firewall on or off.
    4. Select On.
    5. Click OK.
    To turn on the Internet Connection Firewall in Windows XP
    1. Click Start, and click Control Panel.
    2. Click Network and Internet Connections. If you do not see Network and Internet Connections, click Switch to Category View.
    3. Click Change Windows Firewall Settings.
    4. Select On.
    5. Click OK.
    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.
     
    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.
    To turn on Automatic Updates in Windows Vista
    1. Click Start, and click Control Panel. 
    2. Click System and Maintainance.
    3. Click Windows Updates.
    4. Select a setting. Microsoft recommends selecting Install updates automatically and choose a time that is convenient for you. If you do not choose Automatic, but you choose to be notified when updates are ready, a notification balloon appears when new downloads are available to install. Click the notification balloon to review and install the updates.
    To turn on Automatic Updates in Windows XP
    1. Click Start, and click Control Panel. 
    2. Click System.
    3. Click Automatic Updates.
    4. Select a setting. Microsoft recommends selecting Automatic. If you do not choose Automatic, but you choose to be notified when updates are ready, a notification balloon appears when new downloads are available to install. Click the notification balloon to review and install the updates.
    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 that is updated with the latest signature files. Antivirus software is available from several sources. For more information, see http://www.microsoft.com/protect/computer/viruses/vista.mspx.
    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 system 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 in order to compromise a system, they also attempt to exploit vulnerabilities in human behavior in order to do the same. When an attacker attempts to take advantage of human behavior in order 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 system. 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.

    How to Tell If Your Computer Is Infected

    Symptoms of a Win32/Alureon infection may vary according to the particular variant.

    How to Recover from Infection

    Automatic Recovery
    To attempt to automatically remove this threat, run one of the following removal tools:

    Manual Recovery

    The Win32/Alureon trojan may enable an attacker to transmit malicious data to the infected computer. Recovering from this situation may require measures beyond removing the trojan itself from the computer. Use Microsoft Windows Defender, Microsoft Security Essentials, the Windows Live safety scanner, or another up-to-date scanning and removal tool to detect and remove this threat and other unwanted software from your computer. For more information on Microsoft security products, see http://www.microsoft.com/protect/products/computer/default.mspx.
     
    The Domain Name System (DNS) is used (among other things) to map domain names to IP addresses - that is, to map human-readable domain names to machine-readable IP addresses. When a user attempts to visit a particular URL, a browser will use DNS servers to find the correct IP address of the requested domain. When a user is directed to a malicious server that is not part of the authoritative Domain Name System, an attacker can provide incorrect IP addresses at their choice to map to particular domain names, thus directing the user to possibly bogus or malicious sites without the affected user's knowledge.
     
    Win32/Alureon may modify DNS settings on the host computer, thus the following steps may be required after the Win32/Alureon removal is complete:
    • If the computer has a network interface that does not receive a configuration using DHCP, reset the DNS configuration if necessary. For information on configuring TCP/IP to use DNS in Windows XP, see http://support.microsoft.com/kb/305553
    • If a dial-up connection is sometimes used from the computer, reconfigure the dial-up settings in the rasphone.pbk file as necessary, as Win32/Alureon may set the fields "IpDnsAddress" and "IpDns2Address" in the rasphone.pbk file to the attacker's address. The Microsoft scanner code that automatically removes Win32/Alureon backs up the infected dial-up configuration file to:
      %allusersprofile%\Application Data\Microsoft\Network\Connections\Pbk\rasphone.pbk.bak

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