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Win32/Alureon

First posted on 17 April 2012.
Source: Microsoft

Aliases :

Win32/Alureon is also known as TR/Dldr.DNSChanger (Avira), Win32/Alureon (CA), Trojan.DnsChange (Dr.Web), Trojan.Zlob (Ikarus), Trojan-Downloader.Win32.Zlob (Kaspersky), DNSChanger (McAfee), Troj/Zlob (Sophos), Trojan-Downloader.Win32.Femad (Sunbelt Software), Trojan.Zlob (Symantec), TROJ_DNSCHAN (Trend Micro).

Explanation :

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. It 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. Win32/Alureon may also infect and corrupt certain driver files, causing them to become unusable.
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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. It 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 disinfection. Instances of the Win32/Alureon trojan may contain various malicious components. The following are three examples of these 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: HKLM\System\CurrentControlSet\Services\Tcpip\Parameters
• Modify registry values:
  "NameServer"
  "DhcpNameServer"
  under certain subkeys of the subkey:
  HKLM\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, and Vista is:

• %allusersprofile%\Application Data\Microsoft\Network\Connections\Pbk\rasphone.pbk

To allow 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 - <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, and 7 is C:\Windows\System32.
• Inject threads into local processes to delete itself and perform other tasks.
• Create registry entries under the key HKCR.
• Create registry subkeys such as: HKLM\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
  HKLM\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: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

• Delete the following registry entries under subkey HKLM\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 trojan file that is running.

Recent variants of Win32/Alureon may be capable of infecting the miniport driver associated with the hard disk of the operating system, causing the driver file to become corrupted and unusable. For the most common system configuration, that is, for computers using ATA hard disk drives, the ATA miniport driver "atapi.sys" is the target driver file. However, other files may also be targeted. The top ten most commonly-targeted driver files are the following: atapi.sys iastor.sys iastorv.sys idechndr.sys nvata.sys nvatabus.sys nvgts.sys nvstor.sys nvstor32.sys sisraid.sys Some Win32/Alureon components may disable or clear the existing Internet Explorer proxy settings.

Last update 17 April 2012

 

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