A company accused of running an adware scam which infected 15 million PCs has settled its case with the US Federal Trade Commission (FTC).

The owner of ERG Ventures has agreed to pay a $330,000 penalty and follow stricter distribution guidelines in the future.

The FTC alleged that ERG used seemingly harmless software downloads, such as screen savers and video files, to mask covert installations of the Media Motor adware program.

The covertly installed software proceeded to disable any antivirus or adware-blocking software installed on the user's computer and initiate a series of malicious installations.

These included tracking software, pop-up generators and other pieces of malware that slowed performance and changed system settings.

The FTC said that the software hid itself in installations performed with user consent, and was loaded even when users declined to have the original piece of software installed.

Once installed, Media Motor was "extremely difficult or impossible" for users to remove, according to the FTC.

The use of deceptive installation methods has led to several high-profile cases recently.

Adware vendor Zango was hit with a $3m fine in November 2006 for unauthorised installations performed by some of its affiliate vendors.

Video download network Movieland agreed in September 2006 to pay consumers more than $500,000 after the FTC charged that it had used unnecessarily invasive and disruptive billing software.