General OS X Security
When many people get Mac computers for the first time, they jump right into using OS X, but never take the time to adjust Mac internet security and advanced settings. Adjusting these settings on your Mac computer will adjust how OS X works. Thus, improving overall security. Although some of these settings do not directly improve internet security, they are still good to adjust, as they effect OS X as a whole. The majority of these settings will improve OS X internet security in one way or another.
To start, open up your Mac's system preferences by clicking the system preferences icon in the dock. If you have removed the system preferences icon, you can navigate to it using the path: Finder > Applications > System Preferences.
Adjust OS X Security Options:
From within System Preferences, click the Security icon. Under the first tab, General, make adjustments to the settings to fit your own preferences. After you are finished, click the next tab, FileVault.
FileVault is a setting that will encrypt all of the data in your home folder. Should you ever get hacked, encrypted files will be unreadable to the person who steals them. FileVault is not always necessary, although it is a nice precaution to have. If you want to encrypt you home folder, click the Turn on FileVault button. You also have the option to set a master password from the FileVault tab. If you wish to set a password to be used for all accounts on your Mac, go ahead and set the password. Do not lose it!
Click the Firewall tab. The Firewall is going to help improve internet security on your Mac. Click the advanced button. Under the advanced drop down menu, put a check mark next to "Block all incoming connections" and "Enable stealth mode". Upon doing so, you will get the following message:
The firewall will block all sharing services, such as file sharing, screen sharing, iChat Bonjour, etc.
Read this message and assure that you are fine with everything before choosing to Block all incoming connections. Press the OK button when you are finished. If your firewall is not on, make sure that you click the Start button to start your firewall.
Adjust OS X Sharing Options:
From System Preferences, click the Sharing icon. Within this window, you should see several services listed along the right hand side. For example, DVD or CD Sharing, Screen Sharing, File Sharing, Printer Sharing, etc. You can click on each one of these settings to see more details and configure advanced options. To turn a service completely on or off, simply click next to the service to check or uncheck a service. When you are finished, you can exit the System Preferences window.