The problem is Apache HTTP Server contains a bug in the routines which deal with invalid requests which are encoded using chunked encoding. This bug can be triggered remotely by sending a carefully crafted invalid request. This functionality is enabled by default. The child process handling the request will terminate. Which will cause the parent process to start a new child process that eventually uses up system resources. There is currently no patch that works. Apache is working on a version fixed to take care of the bug check <a href="http://httpd.apache.org/" target="_blank">http://httpd.apache.org/</a> for updated versions when they become availabale