Researchers from Proactive Risk, an IT security firm, will demonstrate at an upcoming application security conference a systemic flaw in the HTTP protocol that can easily be exploited through online gaming and other activities into distributed denial-of-service (DDOS) attacks that can flood web servers -- even through secure connections -- with very slow "POST" traffic that is difficult to distinguish from legitimate traffic, making it hard to prevent.
The demonstration will come November 8th at the OWASP 2010 conference in Washington DC and is led by researcher Wong Onn Chee, who first discovered the attack last year in Singapore, according to a report from Dark Reading, a security-focused web site. The technique can crash both IIS and Apache servers using either HTTP or HTTPS protocols, and could conceivably affect anything using a web connection, including SSL, VPN and other "more secure" systems.
Onn Chee and Proactive Risk founder Tom Brennan will show members at the conference how the technique works using a Java applet that runs a game, how it could be used to recruit bots into an "agentless" botnet and attack servers while the players are playing. Brennan and Onn Chee will also solicit for ways to mitigate the risk. The actual fix would involve changing the HTTP protocol, since it is a "critical" flaw in internet infrastructure "by design." The "slow POST" technique could be adapted to also work on SMTP and possibly DNS servers as well.
As described by Onn Chee, the attack works by sending POST headers with legitimate "content-length" fields to let the server know how much data is arriving, but once the headers are sent, the actual body of the message is transmitted at very slow speeds, creating gridlock and tying up resources. In practice, a relatively small quantity of bots doing this (tens of thousands) could disable a server within minutes. Load-balancing software in wide use now to prevent similar DDOS attacks will not be effective against this technique.
So far, this form of attack has been rarely seen outside China, but the "agentless" nature of the attack makes it effective, difficult to prevent and difficult to trace, ensuring it will spread.