Attention at the most recent Apple event was squarely focused on products, particularly the new iPad Pro range and Apple’s new location tracking device, the AirTag. On the software front, iOS 14.5 has stolen all the headlines as it increases user privacy by blocking invasive ad tracking on iPhones and iPads.

Far less publicised has been the release of some updates for MacOS which runs on Apple’s iMac and MacBook computers. While people have been eagerly updating their iPhones, they may have overlooked their computers – and that could be a serious mistake.

Dealing with a zero-day exploit

A new update has been released for MacOS Big Sur (11.3) and, somewhat unusually, for the two previous operating system versions (Catalina and Mojave). These updates address a number of security issues, the most important of which is a zero-day exploit that could leave your computer wide open to hackers and malware.

MacOS is designed to be highly secure, making it as hard as possible for hackers to break into your computer. One core protection is Gatekeeper, a security feature that checks every item of software you ever download and install is legitimate and safe.

However, the developers of the Shlayer trojan had found a way to bypass Gatekeeper so that the malware could install itself undetected. This zero-day exploit was so successful that around 10% of all Mac computers were suspected to have been infected by the Shlayer trojan before security researchers realised there was a problem.

A very, very important update

MacOS updates usually contain a number of patches to address important yet obscure, low level security vulnerabilities – as does MacOS 11.3. But because this latest Big Sur version fixes a significant issue with Gatekeeper, it is even more important that you download and install it as soon as possible. The longer you leave your computer unpatched, the longer you are at risk of being infected by Shlayer or other Mac malware.

Not running MacOS Big Sur? You should still check to see if there are updates available for your Mac because the Gatekeeper exploit also affects previous versions of the operating system.

Simply click the Apple logo in the top left-hand corner of your screen and select About This Mac. A small window will pop-up telling you which version of MacOS is installed. Click the button labelled Software Update… and your computer will see if there are any new patches that need to be installed.

If you want MacOS to install updates automatically in future, tick the Automatically keep my Mac up to date checkbox on the Software Update screen. Your computer will then download updates when they are available and install them overnight ensuring MacOS is kept up to date – and that the installation process doesn’t interrupt when you are using the device.

And as always, keep an eye on the Panda Security blog for the latest news about threats and updates that will help you keep your Mac safe.