www.websitedefender.com
New research reported by the BBC found the sites, visited by millions of people every day, hosted embedded advertisements which put users at risk.
Conrad Longmore, who conducted the research, found popular sites xhamster and pornhub were the greatest threats to users, and said mechanisms should be set up to allow users to report malicious advertising.
“We call these malicious advertisements 'malvertising',” Longmore said. “The way the ads are bought and sold across all websites is incredibly complex.
“Ads can often be repackaged and resold so that it is hard to tell where they originated from, and the criminals behind them go to great lengths to disguise what they are doing.”
Longmore’s data found xhamster, which is listed by monitoring firm Alexa as the 46th most popular site on the internet - carried malicious advertising on five per cent of pages screened in the past 90 days, meaning a 42 per cent risk of users being affected.
pornhub had dangerous advertising on 12.7 per cent of its pages.
“There seems to have been a sudden spike in malware on popular sites, especially in the past week or so,” he said.
He said users should not be afraid to “kick up a fuss”, as otherwise malvertising would continue to go unreported.
“Part of the problem is that porn is a taboo subject,” he said. “But the reality is that these are hugely popular sites with many of them in the top 100 most popular sites globally.
“Site operators could put a quick reporting mechanism on their sites to flag up bad ads and other concerns, and ad networks should also take some responsibility here.
“I don't see that happening any time soon, and perhaps the best thing that users of these sites can do is ensure that their machines are up to date.”
