In an effort to cut off funding for questionable adware vendors, the Center for Democracy & Technology (CDT) has published a list of companies that purchase advertising on adware networks. 

The CDT claims that companies including Altrec, Club Med Americas, eHarmony, Greetingcards.com, Letstalk.com, NetZero, ProFlower, PeoplePC, PerfectMatch, True.com, uBid and Waterfront Media create an incentive for botnet operators to break into computers.

Spyware researcher Ben Edelman has posted images of the offending advertisements on his website. The list is a sample of advertisers that were found using adware from 180solutions. 

They were contacted by the CDT prior to the publication of the report but, with the exception of eHarmony, did not respond. The latter lacks a policy prohibiting the placement of its online ads through adware.

180solutions is one of the world's largest adware networks and in the past year has attempted to rid itself of the adware reputation by suing distributors and making it easier to remove the software.

The CDT, however, claims that these efforts are merely window dressing and earlier this year filed a complaint against the company with the Federal Trade Commission (FTC).

The CDT said that it considers its report a final warning to advertisers, and said that it will lobby the FTC to start publicly naming companies that deal with adware makers if advertisers fail to change their practices.

"Knowingly or not, these companies are fuelling the spread of unwanted programs that clog people's computers, threaten privacy and tarnish the internet experience for millions," said Ari Schwartz, director at the CDT.

He added that many advertisers might not know that they advertise through spyware and adware because ad agencies tend to build chains of partners that pass on purchase orders.

Adware is designed to serve advertisements to the user, often through pop-ups, and is based on the sites that a user visits. The software also typically collects information on surfing habits.

The software is controversial because it uses deceptive practices to get itself installed. Adware distributors often cloud the true intentions of their applications, which often come bundled with free games or other free software.

Botnet operators are also known to install adware on computers in their networks because the adware distributors offer money for each installation.

The CDT praised large online advertisers including Dell and Major League Baseball for creating policies that prohibit the placement of their ads on adware networks.