Malware ads hit London Stock Exchange Web site

Visitors to the London Stock Exchange's Web site were hit with malicious ads over the weekend, designed to pop up fake security messages on their computers.

The culprit was an online advertisement that was somehow placed on the Unanimis ad network, which is used by the the Web site, a London Stock Exchange spokeswoman said Monday. "We had an advert on the site that linked through to a third-party website that was hosting this malware," she said. She did not know how many people had been served the malicious ad.

The Stock Exchange's Web site itself was not compromised, and the ad was removed as soon as it was discovered on Sunday, she said. Nevertheless, visitors to the site early Monday were greeted with browser warnings saying that londonstockexchange.com had been reported as an attack page. The warnings showed up in the Firefox, Chrome and Safari browsers, but were removed later in the day.