In less than a day, CloudCracker can reliably break Microsoft's Challenge Handshake Authentication Protocol version 2 (MS-CHAPv2) -- the basis for key exchange in many popular implementations of VPNs based on the point-to-point tunneling protocol (PPTP). The new functionality reliably recovers the keys used in a session by using brute force enumeration of all possible keys.
Like many dual-use hacking tools, password-cracking services are often blamed for making it easier for attackers to break into networks and Web sites, but the cloud service helps point out insecure protocols, Marlinspike said.
"What we are trying to do is eliminate the use of MS-CHAPv2 -- put this protocol to bed for good," Marlinspike said. While many people believe that the protocol can be used with a large enough passphrase to be secure, it's not true, he said. "No matter what password you choose, we can always get your traffic."
Using online password crackers is nothing new. In fact, CloudCracker started out in 2009 as WPACracker, a service focused on finding the encryption keys used to secure wireless networks. Now CloudCracker includes methods for finding keys to five different types of protocols.
Using the service can help information security managers to illustrate security problems to their users and executives, Marlinspike said. The security researchers have received messages from network administrators responsible for securing the wireless network and who have pushed for stronger authentication technologies.
"They say, 'Look, no one has listened to me because I have not been able to demonstrate that it's possible to crack, but now I'm able,'" Marlinspike said. "So it is helping people make internal cases for taking a little bit more time to deploy a secure solution."
By using a cloud service to crack encryption, companies can benefit from the latest technologies, such as computing systems built from large clusters of specialized hardware. While many companies could build their own systems, cloud services are an inexpensive way to test security and make a point, says Olga Koksharova, marketing director for Elcomsoft, a Russian provider of encryption-cracking software.
Custom built crypto-breaking systems can require "big networks or good hardware accelerators to make it really fast," she says. "These things can be available to a company or a governmental structure, but not to an average person."
[ An assault on one Internet infrastructure provider shows that companies have to pay attention to how their security services are locked down and how the credentials for those services can be recovered. See Attackers Turn Password Recovery Into Backdoor .]
CloudCracker has an easy-to-use front end that allows users to queue up jobs for the system at $17 each. On the back end, the system uses a cluster of field-programmable logic arrays (FPGAs) -- integrated circuits that can be reconfigured for each application -- to crank through 18 billion keys per second. At that speed, breaking an MS-CHAPv2 session takes less than half a day on average. The system is hosted by Pico Computing, a company that builds FPGA systems for encryption applications.
Other security researchers and hacking groups have put similar -- if less user-friendly -- systems online, such as Shmoo's precomputed rainbow tables, which allow fast dictionary attacks and John the Ripper, a popular password cracking program. Using a service is not always best, says Alexander Peslyak, founder of Openwall, the developer of John the Ripper.
"In some cases -- especially with free services -- [a drawback is the] lack of assurance and/or information on what exact categories of passwords have been tested," says Peslyak, well-known online as Solar Designer.
Finally, the perception that cloud services enable attackers to more easily crack passwords is not accurate, Elcomsoft's Koksharova says. Criminals are far more likely to attempt to socially engineer passwords from victims than use a password-cracking service, especially a for-pay service, she says.
"In reality, no real attacker will use password cracking to get access to restricted info, just because it's time-consuming and expensive," she says.
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