In one of the biggest malvertising campaigns in the last 18 months, a previously known threat group called eGobbler is taking advantage of a security bug in Google's Chrome browser to target millions of iOS users.
Security vendor Confiant, which has been tracking the campaign since it launched April 6, estimates that more than 500 million malicious ads have been served to iOS users already. Users are being redirected to scam "You've won a gift card" landing pages hosted on a top-level domain previously associated with eGobbler.
Google, which makes most of its money from online advertisements, is currently working on a fix for the bug after being notified about the issue April 11, Confiant said in a report Tuesday. The company did not respond immediately to a request for comment.
According to Confiant, the problem exists in the manner in which Chrome for iOS handles pop-ups. Like other browsers, Chrome incorporates ad sandboxing features to ensure that any code used to insert ads into a Web page only has limited ability to interact with other components.
Sandboxing is a method of restricting what actions are available to any advertisement that is served from a different domain than the page hosting it, says Eliya Stein, senior security engineer at Confiant. The goal is to prevent malicious advertisements from hijacking browser sessions via pop-ups and redirects to websites and landing pages the user did not intend to visit.
Normally, an ad sandbox should prevent a pop-up from being launched unless the user takes some direct action to enable it. The Chrome vulnerability allows attackers a way around this protection.