OSX Security Threat
Security researchers at SecureMac have discovered Mac OS X malware, capable of taking control of a victim's computer. This Trojan has been given a "critical" security rating.
A Trojan is a program that appears legitimate, but performs illicit activity when it is run, such as stealing passwords, making the system more vulnerable to future entry, or destroying your programs or data. MacScan 2.5, from SecureMac, is a free trial download that can detect and remove the Trojan. For more details, see these two articles:
Mac OS X Security Threat Discovered
Tiny Trojan Trots Into Mac OS X Turf