A development machine should be secured against threads as well as any other machine (or even especially a development machine). Therefore we should install
Head over to Avira, download and install their latest free package.
This one is a bit controversial. If you do not install software which allows network access of any kind, skip it. If you run potentially vulnerable software you don't want to be accessed from other machines, consider turning the built-in firewall on. This particularly applies if you develop network software.
To turn the built-in firewall on:
The last step disables automatic access for software from the App Store. From now on you can either add (dis)allowed programs to the list within the Firewall Options or just click on Allow\/Deny, if you get a popup asking you if a specific software may be accessed.
Another controversial point. If you have a desktop machine in a secured building, you probably do not need disk encryption. If you travel a lot and take your notebook with you (including all your source codes), you should perhaps travel with disk encryption enabled. I cannot tell the impact of disk encryption on system performance because I never used my MacBook unencrypted.
The following steps were taken from the official apple support page on this: