A PDF titled “Hardening tips for OS X Snow Leopard”, the file is free for anyone to grab. Here it is (direct PDF link).
It spells out a lot of simple steps you can take to “harden up” your Mac from security threats. Following them all won’t guarantee that your Mac is safe from every threat out there, but it will make life harder for the malware merchants.
Some of it is good old-fashioned common sense. Stuff like keeping your Mac’s software up-to-date, disabling automatic login, and unchecking Safari’s “Open ‘safe’ files after downloading” preference.
Other tips in the PDF might seem a little over-the-top, especially for ordinary folk. Stuff like disabling Bluetooth and Airport, for example. That’s going to make it tricky to reach Facebook. Remember, though, this is an NSA document for NSA people. You can’t blame them for being more paranoid than most of us.
The recent scares have been about “trojan horse” attacks, and the deal with trojans is that they rely on people’s weaknesses. They’re not taking advantage of holes in OS X, but of people just not thinking before they click.
If anything, that’s the lesson for everyone, not just Mac users: think before you click. Be wary of weird, unexpected, or too-good-to-be-true things that get waved under your nose by the internet. Don’t enter your password if asked for it unexpectedly, don’t enter personal info like passwords or credit card details anywhere unless you’re certain that you’re at the right place.