Unrecognised device appears on startup and then disappears

Hi,
Recently I updated to WiFi Guard 2.2.1 and noticed some weird behaviour: soon after starting my MacBook Pro M1, WiFi Guard displays a message alerting of an unrecognised device (sometimes 2 devices). But if I then open WiFi Guard and press "Scan Now", it shows no unrecognised devices.

Initially, I changed the router's password every time the message was displayed, but then I realised there was a pattern: computer turned on - then the alert message. It is an unexpected and unsettling event and I look forward to your comments.

Regards,
Eduardo

Based on your description, it seems that your issue might be due to your MacBook Pro M1 switching between MAC addresses.

Modern devices like MacBook Pro M1 sometimes use a random MAC address when they initially connect to a network, and then switch to their permanent MAC address once the connection is established.

If your MacBook's permanent MAC address is already whitelisted in WiFi Guard, the program would not identify it as an unknown device, hence no unrecognised devices appear after scanning. However, the initial random MAC address may be triggering the alert that you are seeing, as it would be new and unfamiliar to the app.

A possible solution would be to open WiFi Guard settings - Advanced tab, and disable Instant detection of new devices joining the network. This change will prevent the app from displaying the alert when a new device (like your MacBook Pro) initially enters the network. But you will still have the ability to keep an eye on the devices in your network by performing regular scans.

One clarification on my description of the reported issue: MacBook Pro M1 is the device where WiFi Guard is installed and run, not the reported unidentified device.

To investigate this issue further, I ran WiFi Guard after disconnecting and re-connecting to my network each of my known devices. Eventually, I found out that the reported unrecognised device was my known HP OfficeJet printer.

For some reason, Wi-Fi Guard 2.2.1 displays two entries for this OfficeJet printer. The first entry identifies the printer as a known device with the correct MAC address F8:B4... The second entry shows the printer as an unknown device with a MAC address 01:00... (NB: WiFi Guard always reports this "unknown device" with the same IP address 224.0.0... and MAC address 01:00:5E...)

Disabling the Instant Device Detection option works OK, but I would rather have this option enabled so WiFi Guard can alert me every time an unknown device is connected to my network.

Thank you very much for the detailed clarification. Your meticulous detective work has provided some valuable insights into the issue you are experiencing.

Based on this information, we have made some improvements and published an update to WiFi Guard that should resolve this issue. Please download the most recent build, try it on your system, and let us know how it works for you.

The most recent build works fine on my system - no 'unknown device' messages.

Thank you for the update. It works well for me too!