Massachussets, April 8:

Is your personal computer (PC) a member of an international crime syndicate? Before you laugh, consider this: computer security experts believe that atleast 10 per cent of home PCs have been recruited into robot networks, or ‘botnets,’ under the control of criminals. Botnets are assembled through the distribution of a computer virus over the internet.

If the virus finds its way on to your PC — through a downloaded file, say, or a spam email — it secretly installs a few lines of software code on to your hard drive. The hidden programme allows your machine to be manipulated by a distant computer.

It’s long been possible, of course, to control networked PCs from other computers by using popular ‘remote access’ programmes like GoToMyPC or LapLink. The crooks who run botnets take this useful capability and twist it to their own nefarious purposes. They turn innocent PCs into remote-controlled zombies.

A single botnet can include tens of thousands of computers, and the malicious networks are proliferating rapidly. Vint Cerf, one of the inventors of the internet and now a top Google executive, told the World Economic Forum in February that botnets have become a ‘pandemic’. He estimated that more than 100 million PCs have already been infected.

Another speaker at the forum, New York Times technology writer John Markoff, added, “It’s as bad as you can imagine — it puts the whole internet at risk.” Most botnets today are used to distribute spam.

A spammer can instruct a mob of hijacked computers to pump out millions of messages simultaneously, and because the messages are sent through the email programmes of ordinary citizens, they often slip past spam filters. Botnets are believed to beresponsible for at least 80 per cent of all spam.

Botnets can be put to far darker purposes as well. The programme installed by a botnet virus can, for instance, search a PC’s hard drive and monitor its user’s keystrokes, gathering private data and sending it back over the internet to its master.

In 2006, a network security professional intercepted a large file created by a botnet and examined its contents. He found that it contained sensitive financial information, including credit card numbers and passwords for bank accounts, that had been collected from nearly a thousand infected PCs.