The Conficker worm, sometimes called Downadup or Kido has managed to infect a large number of computers. Specifics are hard to come by, but some researchers estimate that millions of computers have been infected with this threat since January. If you are unable to reach certain web sites, you may be infected. In that case you will need to get to a computer that is not infected, download the Conficker removal tool and run it on the infected machine before new antivirus software. Symantec has created a detailed technical analysis of the threat here.

What does the Conficker worm do?

The Conficker worm has created secure infrastructure for cybercrime. The worm allows its creators to remotely install software on infected machines. What will that software do? We don’t know. Most likely the worm will be used to create a botnet that will be rented out to criminals who want to send SPAM, steal IDs and direct users to online scams and phishing sites.

The Conficker worm mostly spreads across networks. If it finds a vulnerable computer, it turns off the automatic backup service, deletes previous restore points, disables many security services, blocks access to a number of security web sites and opens infected machines to receive additional programs from the malware’s creator. The worm then tries to spread itself to other computers on the same network.

How does the worm infect a computer?

The Downadup worm tries to take advantage of a problem with Windows (a vulnerability) called MS08-067 to quietly install itself. Users who automatically receive updates from Microsoft are already protected from this. The worm also tries to spread by copying itself into shared folders on networks and by infecting USB devices such as memory sticks.

Who is at risk?

Users whose computers are not configured to receive patches and updates from Microsoft and who are not running an up to date antivirus product are most at risk. Users who do not have a genuine version of Windows from Microsoft are most at risk since pirated system usually cannot get Microsoft updates and patches.

More infomation is avalible on  Wikipedia.

The Fix

If you have a computer that is infected, you will need to use an uninfected computer to download a specialised Conficker removal tool from here.

FAQ
Q: What should I do if my PC is infected?

A: If you have a computer that is infected, you will need to use an uninfected computer to download a specialised Conficker removal tool from here.

Q: Am I safe if I don’t go to questionable web sites?

A: No. The Conficker worm seeks out computers on the same network. You can be in a coffee shop, an airport or in the office and the worm will quietly try to attach to your computer and run itself.

Q: How do I know if I am infected?

A: The best way to know if you are infected is to run a good antivirus product. One symptom that may indicate you are infected is finding that your computer is blocked from accessing the web sites of most security companies.