The FBI's DNSChanger deadline extension has been approved by a US Federal Court, buying infected punters more time to clean up their systems.
The move means that machines riddled with the Trojan will still be able to use temporary DNS servers to resolve internet addresses until 9 July. Before the order was granted, infected machines would not have been able to surf the web or handle email properly after 8 March, the previous expiry date of the safety net.
Deployed initially by cyber-crooks, DNSChanger screwed with domain name system (DNS) settings to direct surfers to rogue servers - which hijacked web searches and redirected victims to dodgy websites as part of a long-running click-fraud and scareware distribution scam.
The FBI stepped in and dismantled the botnet's command-and-control infrastructure back in November, as part of Operation GhostClick.
To keep nobbled computers working properly, legitimate servers were set up by the Feds to replace the rogue DNS servers, under the authority of a temporary court order that has now been extended. But this effort did nothing by itself to clean up infected machines.
As many as four million computers were infected at the peak of the botnet's activity.
An updated study by security firm Internet Identity revealed that there has been a "dramatic decrease" in the number of Fortune 500 companies and US federal agencies with DNSChanger on their networks.
IID found at least 94 of all Fortune 500 companies and three out of 55 major government entities had at least one computer or router that was infected with DNSChanger as of 23 February, 2012. This is a sharp drop from the 250 out of 500 Fortune 500 companies found to be infected a few weeks prior to its latest survey – providing evidence that the clean-up operation has finally clicked into gear.
More information on how to clean up infected machines, and other resources, can be found on the DNS Changer Working Group website here. ®