This article is from the Miscellaneous Macintosh FAQ, by Elliotte Rusty Harold email@example.com with numerous contributions by others.
a password. Some of the more easily defeated products, mostly
shareware, use a system extension or startup application to display
a splash screen that doesn't go away until the proper password is
entered. Most of these can be bypassed by any of several methods
including booting off a floppy or a different SCSI device,
disabling extensions with the Shift key at Startup, or even
dropping into the built-in debugger.
Products that are more difficult to defeat (mostly payware)
don't allow a hard disk to be mounted until the proper password
is entered. Most of these can be defeated by loading a different
driver with a hard disk formatter like FWB's Hard Disk Toolkit
after booting from a floppy. No program of this type provides
hacker-proof security. Nonetheless the better programs do provide
a minimum level of protection from casual snoopers or intruders.
My choice of commercial products in this category is Citadel
from Datawatch ($60 street). Citadel is a complete Macintosh
security program that provides password protection for hard disks,
file and folder protection via DES encryption, screen locking, and
the best protection I've ever seen against accidentally locking
yourself out of your hard drive while still keeping intruders out.
It's not totally intruder-proof, (No such product is.) but it does
provide more reliable protection and more value for the money than
any similar product I'm aware of. Some hard disk formatters also
offer optional password protection. Notable in this category is
FWB's Hard Disk Toolkit Personal Edition, about $50 mail-order.