Threat Description

Trojan:​W32/DNSChanger

Details

Aliases: Trojan:W32/DNSChanger, Win32/Alureon
Category: Malware
Type: Trojan
Platform: W32

Summary


DNSChanger is a trojan that will change the infected system's Domain Name Server (DNS) settings, in order to divert traffic to unsolicited, and potentially illegal sites.



Removal


Automatic action

Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.

More

Detailed instructions for F-Secure security products are available in the documentation found in the Downloads section of our Home - Global site.

You may also refer to the Knowledge Base on the F-Secure Community site for further assistance.



Technical Details


The trojan is usually a small file (about 1.5 kilobytes) that is designed to change the 'NameServer' Registry key value to a custom IP address. This IP address is usually encrypted in the body of a trojan. As a result of this change a victim's computer will contact the newly assigned DNS server to resolve names of different webservers.


Variant: Trojan.Win32.DNSChanger.al

Lately we got a few samples of this trojan that were named 'PayPal-2.5.200-MSWin32-x86-2005.exe'. This trojan was programmed to change the DNS server name of a victim's computer to 193.227.227.218 address. The Registry key that is affected by this trojan is:

  • [HKLM\SYSTEM\ControlSet001\Services\Tcpip\Parameters\Interfaces] "NameServer"
Registry Modifications

Creates these keys:

  • HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{random}DhcpNameServer = 85.255.xx.xxx,85.255.xxx.xxx
  • HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{random}NameServer = 85.255.xxx.133,85.255.xxx.xxx
  • HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\DhcpNameServer = 85.255.xxx.xxx,85.255.xxx.xxx
  • HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\NameServer = 85.255.xxx.xxx,85.255.xxx.xxx





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