Even though the botnet behind the DNSChanger Trojan was dismantled towards the end of last year, a huge number of enterprises appear to still be infected.

So what's the problem if the power behind the Trojan has been hauled off to jail? Well how about the small matter of the FBI apparently insisting it will seek to disconnect any computer still found to be infected with DNSChanger on 8 March?

DNSChanger was one of the most malicious of Trojans to hit businesses last year, infecting around 4 million computers globally. It worked by changing the host system's Domain Name Server (DNS) settings to point them at assorted advertising and often malicious sites via the now dismantled botnet.It also made changes to ensure that infected systems could no longer access security vendor sites in order to get help with removal of the thing.

DNSChanger was one of the most malicious of Trojans to hit businesses last year.

It was a typically clever bit of malware and one that proved to be pretty successful, allegedly netting the Estonian gang behind it upwards of 8 million in profit. It did all of this by simply changing the NameServer Registry key value to a custom IP address upon installation of the malicious executable.