Trojan.Win32.DNSChanger is a backdoor trojan that redirects users to various malicious websites through the means of altering the DNS settings of a victim's computer. The malware strain was first discovered by Microsoft Malware Protection Center on December 7, 2006[1] and later detected by McAfee Labs on April 19, 2009.[2]
DNS changer trojans are dropped onto infected systems by other means of malicious software, such as TDSSorKoobface.[3] The trojan is a malicious Windows executable file that cannot spread towards other computers. Therefore, it performs several actions on behalf of the attacker within a compromised computer, such as changing the DNS settings in order to divert traffic to unsolicited, and potentially illegal and/or malicious domains.[2][1]
The Win32.DNSChanger trojan is used by organized crime syndicates to maintain click fraud. The user's browsing activity is manipulated through various means of modification (such as altering the destination of a legitimate link to then be forwarded to another site), allowing the attackers to generate revenue from pay-per-click online advertising schemes. The trojan is commonly found as a small file (+/- 1.5 kilobytes) that is designed to change the NameServer registry key value to a custom IP address or domain that is encrypted in the body of the trojan itself. As a result of this change, the victim's device would contact the newly assigned DNS server to resolve names of malicious webservers.[4]
Trend Micro described the following behaviors of Win32.DNSChanger:
HKLM\SYSTEM\ControlSet001\Services\Tcpip\Parameters\Interfaces\NameServerHKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{random}, DhcpNameServer = 85.255.xx.xxx,85.255.xxx.xxxHKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{random}, NameServer = 85.255.xxx.133,85.255.xxx.xxxHKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\, DhcpNameServer = 85.255.xxx.xxx,85.255.xxx.xxxHKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\, NameServer = 85.255.xxx.xxx,85.255.xxx.xxx[6]
