Disinfectant detects all known Macintosh Viruses. (See “Eradication” for more info).
Apple’s Virus RX will detect most known computer viruses as of this writing. It has a good user interface and gives accurate reports, but is updated rather slowly.
Interferon will detect some viruses, but has not been updated in some time and has become badly outdated.
For Commercial Detection programs, see the “Protection” section.