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Hacker pokes new hole in secure sockets layer

Moxie Marlinspike's man-in-the-middle

Website encryption has sustained another body blow, this time by an independent hacker who demonstrated a tool that can steal sensitive information by tricking users into believing they're visiting protected sites when in fact they're not.

Unveiled Wednesday at the Black Hat security conference in Washington, SSLstrip works on public Wi-Fi networks, onion-routing systems, and anywhere else a man-in-the-middle attack is practical. It converts pages that normally would be protected by the secure sockets layer protocol into their unencrypted versions. It does this while continuing to fool both the website and the user into believing the security measure is still in place.

The presentation by a conference attendee who goes by the name Moxie Marlinspike is the latest demonstration of weaknesses in SSL, the encryption routine websites use to prevent passwords, credit card numbers, and other sensitive information from being sniffed while in transit. Similar to side jacking attack from 2007 and last year's forging of a certificate authority certificate, it shows the measure goes only so far.

"The attack is, as far as I know, quite novel and cool," said fellow researcher Dan Kaminsky, who attended the Black Hat presentation. "The larger message of Moxie's talk is one that a lot of people have been talking about actually for a few years now: This SSL thing is not working very well."

Marlinspike said SSLstrip is able to work because the vast majority of sites that use SSL begin by showing visitors an unencrypted page and only offer the protection for sections where sensitive information is transmitted. When a user clicks on a login page, for instance, the tool alters the site's unencrypted response so the "https" is changed to "http." The website, however, continues to operate under the assumption the connection is encrypted.

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