freshclam in ClamAV in Apple Mac OS X 10.5.8 with Security Update 2009-005 has an incorrect launchd.plist ProgramArguments key and consequently does not run, which might allow remote attackers to introduce viruses into the system.
http://support.apple.com/kb/HT4077
http://lists.apple.com/archives/security-announce/2010//Mar/msg00001.html