Malware makes headlines regularly these days, and although Macs are targeted far less than Windows PCs, Mac users still need to remain vigilant. A particularly serious type of malware is called “ransomware” because once it infects your computer, it encrypts all your files and holds them for ransom.

Luckily, despite the virulence of ransomware in the Windows world, where there have been major infections of CryptoWall and WannaCry, only a few pieces of ransomware have been directed at Mac users:

• The first, called FileCoder, was discovered in 2014. When security researchers looked into its code, they discovered that it was incomplete, and posed no threat at the time.
• The first fully functional ransomware for the Mac appeared in 2016, a bit of nastiness called KeRanger. It hid inside an infected version of the open source Transmission BitTorrent client and was properly signed so it could circumvent Apple’s Gatekeeper protections. As many as 6500 people may have been infected by KeRanger before Apple revoked the relevant certificate and updated macOS’s XProtect anti-malware technology to block it.
• In 2017, researchers discovered another piece of ransomware, called Patcher, which purported to help users download pirated copies of Adobe Premiere and Microsoft Office 2016. According to its Bitcoin wallet, no one had paid the ransom, which was good, since it had no way of decrypting the files it had encrypted.

Realistically, don’t worry too much. But it’s likely that malware authors will unleash additional Mac ransomware packages in the future, so we encourage you to be aware, informed, and prepared.

First, let’s explain a few key terms and technologies. Apple’s Gatekeeper technology protects your Mac from malware by letting you launch only apps downloaded from the Mac App Store, or those that are signed by developers who have a Developer ID from Apple. Since malware won’t come from legitimate developers (and Apple can revoke stolen signatures), Gatekeeper protects you from most malware. However, you can override Gatekeeper’s protections to run an unsigned app. Do this only for apps from trusted developers. Even if you never override Gatekeeper, be careful what you download.

Apple’s XProtect technology takes a more focused approach, checking every new app against a relatively short list of known malware and preventing apps on that list from launching. Make sure to leave the “Install system data files and security updates” checkbox selected in System Preferences > App Store. That ensures that you’ll get XProtect updates. Similarly, install macOS updates and security updates soon after they’re released to make sure you’re protected against newly discovered vulnerabilities that malware could exploit.

Also consider running anti-malware software like Malwarebytes. That’s not absolutely necessary, like anti-malware solutions are for Windows, but doing so can provide peace of mind, particularly if you regularly visit sketchy parts of the Internet or download dodgy software. Of course the smarter thing to do is to avoid these sketchy sites in the first place. Don’t ever try to download pirated software.

Although regular backups with Time Machine are usually helpful, KeRanger tried to encrypt Time Machine backup files to prevent users from recovering their data that way. Similarly, a bootable duplicate updated automatically by SuperDuper or Carbon Copy Cloner could end up replacing good files with encrypted ones from a ransomware-infected Mac, or a future piece of ransomware could try to encrypt other mounted backup disks as well.

The best protection against ransomware is a versioned backup made to a destination that can be accessed only through the backup app, such as an Internet backup service like Backblaze (home and business) or CrashPlan (business only). The beauty of such backups is that you can restore files from before the ransomware encrypted them. Of course, that assumes you’ve been backing up all along.

If you ever are infected with ransomware, don’t panic, and don’t pay the ransom right away. Contact us so we can help you work through your options, which might entail restoring from a backup or bringing files back from older cloud storage versions. There are even descriptors for some Windows ransomware packages, and such utilities might appear for hypothetical Mac ransomware as well.

To reiterate, there’s no reason to worry too much about ransomware on the Mac, but letting Apple’s XProtect keep itself up to date, staying current with macOS updates, and using an Internet backup service will likely protect you from what may come.