Avoiding Data Loss with More Security

To prevent data loss on a Mac, especially if it is used in a home office or on the road, it is a good idea to look at the various firewall options. Although the operating system has a built-in firewall, attackers can work around it easily with additional tools. The first thing you should do is check System Preferences | Security & Privacy | Firewall to see whether the firewall is active, which is not the case after installing macOS 11. To enable the firewall, click on the lock icon, enter your Apple ID, and start protection by clicking the Turn On Firewall button, which will make advanced security options available from the Firewall Options button.

An external tool is necessary to keep a general overview of the programs that open Internet connections. Although the macOS built-in firewall blocks incoming connections, it does not give you control over outgoing traffic. The open source LuLu [10] firewall allows more control.

After installing LuLu, you can specify which Apple applications you want the firewall to allow automatically. You can also automatically approve the internal macOS applications and block only external programs. The settings are in the Preferences option under the Shield in the menubar. For each program that tries to establish an Internet connection, a window appears that displays the details, where you can define whether the respective application is allowed to communicate externally. Allow permits the data traffic, whereas Block prevents it. If you want to allow only temporary access, then use the temporarily option. LuLu has a rules menu item that lets you call up the firewall rules to configure access or delete rules. If the application tries to access the Internet again, LuLu displays a window, and you can decide whether to allow or block.

Conclusions

To avoid data loss from the outset, it makes sense to start with system security and keep an eye on the firewall and outbound network traffic. If a mishap does happen, the tools and on-board resources presented here can help you recover data, which is easiest if a data backup with Time Machine has been implemented. See also the "Clean Up and Optimize macOS" box for a way to keep your filesystem orderly.