Security researchers are warning of a fake Adobe Flash Player update extension whose goal is to serve spam ads to victims.
The malicious plug-in, dubbed FlashPlayer11.safariextz, is being distributed from mostly pornographic websites, according to Jerome Segura of security firm Malwarebytes. Unsuspecting users are told they need to “install this update for Flash to view this video", but it is actually a malicious file.
The threat is "widespread", according to a spokeswoman for the company, which is monitoring the outbreak.
Once the bogus software is installed, it displays racy ads.
"For example, I visited PBSKids.org, a site for children to play games and watch their favourite characters, when all of a sudden a pornographic advertisement was displayed," Segura wrote in a blog post.
It's not just lewd ads being served, either. The malware – which does not affect Internet Explorer, but was spotted in Chrome, Safari and Firefox – is also capable of superimposing spam ads over legitimate ones.
"Online advertising is a billion-dollar industry, and everybody wants to have a piece of it," Segura wrote. "With such invasive adverts, cyber crooks are likely to generate a lot of views and even pay-per-clicks. If you believe you are seeing strange or inappropriate ads on the websites you regularly visit, it wouldn't hurt checking the extensions installed in your browser and removing the offending ones."