A German group, The Hacker's Choice, has released an application named THC-SSL-DOS that leverages the computationally intensive processing of Secure Sockets Layer (SSL) negotiations between a client and a server.
The implementation of the secure protocol is such that the handling of SSL connections could require an extensive amount of CPU resources on the server. The application is designed to leverage this behavior by establishing a large number of SSL connections with a server from a single host or multiple hosts. Distributed denial of service (DDoS) attacks could also be conducted using this tool.
Reports indicate that the application is also capable of exploiting the flaw within the SSL Secure Renegotiation feature that could result in large amount of renegotiations via a single TCP connection. A successful exploit could allow the attacker to render the server inaccessible to the Internet, resulting in a DoS condition.
The application is available for Unix as well as for the Microsoft Windows platform and is available as Open-source software.
To mitigate the DoS condition administrators are advised to use SSL Accelerators within the network and disable the SSL Secure Renegotiation feature on affected servers.