Cookie forgery tools pose danger, says researcher

Open source tools let hackers impersonate users

A pair of open-source tools that sniff network traffic for cookies, then use the data to feed those purloined files back to Web sites, will let hackers easily impersonate users, a security expert said yesterday.

The tools, dubbed "cookiesniffer" and "cookieserver" by Michele Dallachiesa, their Italian creator, pose a significant risk to users, said Paul Henry, a vice president at San Jose-based Secure Computing.

"Simply put, cookies are now as susceptible as static passwords in the age of Web 2.0," said Henry in a posting to his personal blog on Monday. "With the release of [these] tools CSRF [cross-site request forgery] is nearing the Script Kiddie level of execution," Henry continued. "Beyond warning users to log off of sites before visiting another and clearing cookie data, serious consideration must now perhaps be given to rewriting Web apps to take advantage of the use of one-time tokens."

Henry's concern stemmed from the two applications Dallachiesa announced Sunday via security mailing lists such as Bugtraq. Used together, cookiesniffer and cookieserver let not-so-astute hackers parse HTML traffic, filter it for cookies -- the small, unencrypted files that many commercial Web sites use to identify returning users -- then reflect those cookies back to the sites.

"With cookieserver, you can impersonate the cookies of someone else in your browser using the logs of cookiesniffer (in [a] few seconds)," Dallachiesa wrote on Bugtraq. "This attack is also called 'side-jacking,' 'cookie replay attack' and 'HTTP session hijacking.' This is something known from 10 years but that is still (too much) effective."

Dallachiesa also posted a list of Web services and sites vulnerable to cookiesniffer/cookieserver. The list included the Italian versions of Yahoo.com and Hotmail.com and the official site of Poste Italiane, Italy's postal service.

Neither Dallachiesa or Henry outlined possible attack tactics, but the former included a link to an August account from the Black Hat security conference held in the US during which another researcher, Robert Graham, the CEO of Errata Security, demonstrated tools that allowed him to snatch cookies from traffic at public wireless hot spots.

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Gregg Keizer

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