A global network of "zombie" computers has been rounded up in Spain. Spanish police say this is the largest network of its kind ever discovered. The police operation was carried out with the assistance of the US Federal Bureau of Investigation.

Three Spaniards were behind the network. They had succeeded in taking control of 13 million computers in almost every country in the world.

They sent viruses to unsuspecting computer users which were designed to steal user names, passwords and credit card details. The information was probably sold for criminal purposes.

Both companies and private individuals were attacked. The computer belonging to the main suspect was found to contain data from 800,000 other computers, including hundreds of large companies and dozens of banks from around the world.