Apple has released a Security Update for OS X 10.2.4.
The update addresses an issue in sendmail in which a remote individual could gain access and control of the system. This feature is turned off by default in Mac OS X, but Apple recommends all users install the update as a precaution.
The update also includes a newer version of OpenSSL providing improved data confidentiality by addressing a "recently-discovered" security issue, says Apple in notes accompanying the release.
This is a 1.7MB update available through the OS's System Update feature or for direct download from the Apple site.