Here are the results of the challenge launched by the Unversity of Wisconsin to test OS X against hacking. "The response has been very strong; traffic to the host spiked at over 30 Mbps. Most of the traffic, aside from casual web visitors, was web exploit scripts, ssh dictionary attacks, and scanning tools such as Nessus. The machine was under intermittent DoS attacks. During the two brief periods of denial of service, the host remained up. The test machine was a Mac mini (PowerPC) running Mac OS X 10.4.5 with Security Update 2006-001, had two local accounts, and had ssh and http open with their default configurations. There were no successful access attempts during the 38 hour duration of the test period."