Joomla! contains a flaw that may allow a remote denial of service. The issue is triggered when an attacker requests an unusually high search number to 'Search Mambots' which causes a search flood to occur, and will result in loss of availability for the service.
Upgrade to version 1.0.4 or higher, as it has been reported to fix this vulnerability. An upgrade is required as there are no known workarounds.