Google finds itself under fire again for helping to spread viruses and malware through AdWords.

Researchers at security software maker Exploit Prevention Labs have uncovered evidence that malware distributors are using Google AdWords to infect computers.

Exploit’s CTO, Roger Thompson said his team discovered many AdWords ads posing as legitimate ads, but then redirecting to more sinister content. He blames Google’s model of taking money first and asking questions later.

“Google says they are doing the best that they can, but their business model is to take as much money as they can for advertisements. No matter how much due diligence they do, it’s a difficult position to be in, but clearly they are not doing enough,” Thompson said.

“If they don’t do a better job of vetting their customers, we will see this sort of thing happening again and again.”

Ad network BlueLithium studied 1.7 billion impressions, from 716 ads, across more than 100 sites, and determined that user-generated content (UGC) generally offered a lower cost per conversion than traditional media.

When comparing ads shown on non-UGC sites (sites with a more structured editorial process) to those sites with UGC, the ads on the non-UGC sites had a 32% higher conversion rate. However, due to the lower advertising costs associated with many UGC sites, the cost-per-conversion on non-UGC sites was 58% higher than the consumer generated alternatives. According to CMO, Dakota Sullivan, the cost savings “more than balanced out” the lower conversion rates of ads running on UGC sites.

BlueLithium also explored UGC against non-UGC sites from the comScore Top 250.