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'Kill switch' flaw found in top web weapon, victims sigh with relief

Turn the tables on DDoSers

Security researchers have discovered a vulnerability in a top DDoS attack tool that provides a handy means to neutralise onslaughts.

The Dirt Jumper Distributed-Denial-of-Service (DDoS) Toolkit is one of the most popular attack tools available. It was deployed in a digital siege against security news website KrebsonSecurity.com among many, many other victims in recent months. The weapon works by instructing an army of compromised computers to flood a website with traffic until legitimate visitors are unable to connect.

However a flaw in the software, uncovered by security researchers at DDoS mitigation specialists Prolexic, can be exploited to thwart assaults.

Armed with the identity of the C&C server or infected host, and open source penetration-testing tools, it is possible to gain access to the database in the system used to control the PC army and, more importantly, the server-side configuration files, Prolexic discovered.

“With this information, it is possible to access the C&C server and stop the attack,” explained Scott Hammack, chief executive officer at Prolexic.

“DDoS attackers take pride in finding and exploiting weaknesses in the architecture and code of their targets. With this vulnerability report, we’ve turned the tables and exposed crucial weaknesses in their own tools,” he added.

The Pandora DDoS toolkit, the latest member of the Dirt Jumper family, is also somewhat buggy.

Pandora can be used to launch five different attack types, including a combination of techniques against the web application and infrastructure layers of targeted websites. Typos in the malware result in broken GET requests. These mistakes are not bad enough to stop a network of compromised machines from launching the distributed attack, but they are severe enough to identify the zombie assailants.

A threat advisory from Prolexic explaining the bugs in both DDoS crimware tools can be found here. ®

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