The Dutch telecommunications watchdog has fined the makers of a group of malicious software programs known collectively as “DollarRevenue” €1 million (US$1.4 million), a spokeswoman said Thursday.

“DollarRevenue” is believed to have been one of the world’s largest spyware distributors when it was active in 2005-2006, infecting 22 million computers globally.

The adware application silently downloaded advertising software and installed it to the computer without the user’s knowledge. DollarRevenue was also bundled with some ad-supported products and was extremely difficult to remove.

The software was also directly linked to certain botnet attacks, with over 7,700 machines hacked within 24 hours.

They managed to install the software on personal computers via downloads from the internet and by exploiting security loopholes in computer programmes. The illegally installed software allowed the companies to spy on consumers’ online behaviour and triggered pop-up windows containing specific advertising material.

The DollarRevenue distributors operated between October 2005 and November 2006. In the summer of 2006, OPTA ordered the companies to cease updating the software or face a fine. DollarRevenue ranked among the top 10 spyware applications worldwide. Users routinely complained about the application on discussion boards and in user forums because the software flooded their PCs with advertisements, effectively rendering them useless.