Although sites from around the world were affected, the vast majority of infected computers were sited in Italy.

"We were referring to it as 'Italian Job 3,' in-house," said David Perry of security firm Trend Micro.

The compromised sites were mainly tourism sites with Italian domains ending in .it such as http://www.adriahotel.it, http://wwww.bestoftuscany.it and http://www.mothertheesacause.info.

"Do not go to these sites," said Perry.

Most of the infected Web sites are legal, Perry emphasised.

"These aren't porn sites, they aren't gambling sites; they are hotels, fish-and-tackle sites, tourist information," he said.

Surfers are only vulnerable if they are using older versions of Microsoft Internet Explorer.

The spyware takes the information from your computer and sends it to a server located in Chicago, USA.

Even if the server is located and shut down, the spyware can be reprogrammed remotely to send it elsewhere.

"Your system belongs to them," Perry said.

"If Chicago is shut down, they could move anywhere in the world."