It can create networks of remotely controlled computers to take part in online attacks, send junk e-mail messages as spam and engage in other shady activities common to the bad neighbourhoods of cyberspace.

The new program, known as 'phatbot' or 'polybot', uses technology like that developed for file-sharing networks like Gnutella and KaZaa to control the machines. ('Bot' is shorthand for 'software robot', a term generally applied to automated software.)

Once the program has made its way onto a victim's computer, it spreads across networks and searches for passwords that are stored on hard drives and are passing across local networks.

It also disables anti-virus programs and systems for upgrading software security.

Phatbot, which is technically known as a computer worm, was considered novel enough that the Department of Homeland Security in the United States asked a group of computer analysts last week to examine and monitor it, said Mr Donald Tighe, a spokesman for the department.

The phatbot program, which was detected by security researchers, was described in an article on the website of The Washington Post on Wednesday morning.

Mr Craig Schmugar, virus research manager with Network Associates, a computer security company, said his company currently rates phatbot a 'low risk', because it has not spread as widely as recent worms, like MyDoom, Netsky and Bagle.

However, he added that 'the potential for this one is huge' because it can spread in many ways and performs many surreptitious functions on the machines.

Mr Joe Stewart, senior security researcher at LURHQ Corp, a company that manages security services for businesses, expressed some surprise over the attention the program has received from the government and anti-virus researchers.

'It's got extra features that make it a little bit more formidable, but it's certainly not a quantum leap in bot technology,' said Mr Stewart, who published a detailed analysis of the new program on his company's website, www.lurhq.com.

Phatbot is a variant of an earlier program known as agobot or gaobot.

It takes advantage of security flaws in Microsoft Windows operating systems that have been exploited by recent Internet viruses such as MyDoom.

Previous bot programs have commandeered large networks of machines.

They have then used them to anonymously send spam, advertise pornographic websites and launch online attacks that block access to websites.

Phatbot is one of a more recent wave that uses technology developed for file-sharing networks.

Earlier programs used a technology for instant online messages called Internet Relay Chat to accomplish the same ends.

Mr Stewart said research showed the program will create networks of as many as 50 computers, far smaller than the networks usually assembled to launch massive attacks on particular websites.

He said it is likely the purpose of these networks, therefore, is to send spam without being detected and without having to pay an Internet service provider.

Any computer that is infected with the new program is probably also burdened with other malicious software, said Mr Stewart.

In that case, he added: 'You've got a lot more to worry about than this.'

Source: New York Times