Stay safe: Malware-preventing software for Macintosh computers (Macs)

If you’re handling sensitive data, you need to keep your computer safe.

First, enable full-disk encryption, which is built in via FileVault, using a password long and complex enough that it’s not easy to break.

Second, visit Objective-See Software for some fine free preventive programs:

BlockBlock informs you when software is trying to install things into the system.
ReiKey looks for anything monitoring your keyboard (to steal passwords and such).
RansomWhere keeps track of any encryption taking places and stops it until you give permission.
Do Not Disturb alerts me if someone’s opened my computer when I’m not around (I normally only use this when I travel).
If you are more of an expert, you can also get LuLu, a free, open-source firewall that alerts you to software trying to contact the outside world, and lets you prevent it from doing so—always good if you've installed anything you're not 100% certain of.

LaunchControl ($15 for personal license, trial available) is very good finding and removing startup software in places that are hard for novice users to find (not free.)

Software which doesn't keep my computer, but does keep me sane:

Alfred (free launcher software, control-space brings up a spot for me to type the first few letters of a file or program to run)
DefaultFolder (makes the open/save dialogue boxes more rational) - expensive but often on sale in cheap bundle plans