Instances of the Win32/Alureon trojan may contain various malicious components. The 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: 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 - 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:
With data:
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 Win32/Alureon 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.
In some instances, Alureon may modify certain driver files such that they become corrupted and unusable. These corrupted files that will NOT be restored by detecting and removing this threat. In order to restore functionality to the computer, the corrupted file must be restored from backup. Users are advised to boot into a recovery environment and manually replace the file with a clean copy.