Ad blocking is an increasing concern for many online publishers, with different companies adopting a variety of approaches to combat the drop in advertising revenues they are facing. Like a number of other websites, Forbes has been asking visitors to disable their ad blockers in order to view content, but in an unfortunate twist, has then almost immediately served up malware pop-unders to readers.

For the past few weeks, visitors with Adblock or uBlock enabled have been greeted with a message telling them to disable their ad blocking programs if they wish to see any content on Forbes. The use of Google cached pages, a common workaround for such barriers, has not worked for ad blocking users thanks to Forbes interstitial Quote of the Day page.

However, those who did deactivate ad blockers were presented with pop-under malware-infected ads (captured above by Twitter user Brian Baskin) which aim to infect computers in order to steal personal information including banking details, or lock up hard drives which can then be ransomed off.

Forbes is just the latest large website to be discovered serving malware-infected ads. Less than a month ago, video site DailyMotion put an estimated 128m users are risk to malware from the Angler Exploit Kit family. Atomx, the online advertising platform that the infected ad came from, blamed a “rogue advertiser” on the WWPromoter network.

Malware from the Angler family also struck users last year, when infected websites including MSN.com, Yahoo, the Daily Mail and Readers Digest, exposing potentially millions of readers to malware.

Even Forbes suffered another similar attack last year, when eight pages on the website began serving up malware infected ads which were connected to the Angler and Neutrino exploit kits.

“Forbes has strict practices in place to protect against these kinds of incursions and will make any necessary changes to be sure such incidents do not occur again,” said a Forbes Media spokesperson at the time.