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Wednesday, March 06, 2013

Cybercriminals Likely To Expand Use Of Browser Proxies

A technique for controlling a compromised system’s browser, widely used in Brazilian banking schemes, will likely become more widespread worldwide in the next few years, say security experts. The technique abuses a legitimate way to control where a browser sends its requests, known as proxy auto-configuration or PAC, to take over a victim’s browser and send traffic—say, requests to a bank—to an attacker-controlled server instead.  While the attackers still have to find a way to execute code on a victim’s system, once that is done, they can set a proxy for the browser, capture selected traffic, and re-route it invisibly.

“You can essentially have the end users interact with a shadow Internet, essentially an Internet experience that is designed by the bad guys,” says Daniel Ingevaldson, chief technology officer for Easy Solutions, a fraud-prevention company that operates extensively in South America. “We haven’t seen anything that sophisticated yet, but I can see a scenario when this attack can be used to implement a server-side or cloud-based man-in-the-middle attack,” Ingevaldson says.

In an analysis of one attack, cloud security firm Zscaler detailed a PAC file that would set a victim’s browser to forward traffic for several Brazilian banking sites and American Express’s site to an attacker-controlled server. With a PAC file, the attackers can be a lot more choosy, redirecting requests to a group of sites or to one site in particular, says Anup Ghosh, co-founder and CEO of Invincea, a firm which detect and blocks Web and e-mail threats.

Preventing PAC files from compromising browsers is not a simple task, as client-side security software will likely find it difficult to detect whether a give PAC file is a valid change or a malicious attack, he adds.

In addition, companies that use a proxy for security or DNS—and so use a proxy auto-configuration file to configure their employees’ browsers—have a good chance of detecting changes that affect their infrastructure.

Link: http://www.darkreading.com/advanced-threats/167901091/security/attacks-breaches/240150191/cybercriminals-predicted-to-expand-use-of-browser-proxies.html.html

Posted on 03/06
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