Most anti-virus software is the worst of both worlds: 1) it fails to block virus, trojans and rootkits, 2) it messes up your operating system (infecting file sy

Most anti-virus software is the worst of both worlds: 1) it fails to block virus, trojans and rootkits, 2) it messes up your operating system (infecting file system hooks). Firewall software can be useful- but less so anti-virus (though you do need to turn off some auto-run/auto-open facilities even on a Mac).