I had a little problem on my MacBook Pro. I had just brought it fully up to date with macOS updates, using downloaded installer packages rather than Software Update, and needed to update Gatekeeper and MRT security data files. I opened LockRattler, and every time that I clicked on the button to List all pending updates, it eventually told me that it couldn’t reach Apple’s update servers.

I checked on my desktop system, which could reach those servers fine. I then tried clicking on the Install all pending updates button instead, but that brought no joy either – again, there was no answer. I then tried Trigger background check, which also drew a blank, even though I knew that both Gatekeeper and MRT were still out of date.

It was then that I noticed TripMode’s menubar icon. I had been reviewing this wonderful product for Mac|Life and MacFormat, and on completing my review had turned TripMode off and quit it. Somehow in the macOS updating process, it had been enabled, and was quietly sitting there blocking the outgoing connections which would have brought me those updates.

Before you try using LockRattler to list or install pending updates, ensure that any firewall which blocks outgoing connections is either disabled, or will allow those connections. This applies not only to TripMode, which limits data transfer to ensure you remain within your mobile connection budget, but also to Little Snitch and Patrick Wardle’s superb open source Lulu firewall.