Now available via Software Update:
Security Update 2004-09-07 delivers a number of security enhancements and is recommended for all Macintosh users. This update includes the following components:
CoreFoundation
IPSec
Kerberos
libpcap
lukemftpd
NetworkConfig
OpenLDAP
OpenSSH
PPPDialer
rsync
Safari
tcpdump
For detailed information on this Update, please visit this website: http://www.info.apple.com/kbnum/n61798
[Update] A revised version (1.1) of the Security Update was made available as of 2004-09-13, apparently to address certain issues that arose from the first release.