CWmike writes "Developers of the Apache open-source project warned users of the Web server software on Wednesday that a denial-of-service (DoS) tool is circulating that exploits a bug in the program. 'Apache Killer' showed up last Friday in a post to the 'Full Disclosure' security mailing list. The Apache project said it would release a fix for Apache 2.0 and 2.2 in the next 48 hours. All versions in the 1.3 and 2.0 lines are said to be vulnerable to attack. The group no longer supports the older Apache 1.3. 'The attack can be done remotely and with a modest number of requests can cause very significant memory and CPU usage on the server,' Apache said in an advisory. The bug is not new. Michal Zalewski, a security engineer who works for Google, pointed out that he had brought up the DoS exploitability of Apache more than four-and-a-half years ago. In lieu of a fix, Apache offered steps administrators can take to defend their Web servers until a patch is available."