1. SentryFi
2. WiFi guides
3. iPhone weak security warning

What triggers the warning

Apple’s guide to router settings says older, deprecated security protocols “are no longer secure, they reduce network reliability and performance, and they cause your device to show a security warning.” It lists the settings that do this:

The same Apple page also explains two related warnings: that your device’s private Wi-Fi address is disabled for a network, and that a network is blocking encrypted DNS. A hidden network (one that doesn’t broadcast its name) can trigger a privacy warning too. These are different problems with different fixes; see the private WiFi address guide and the DNS guides.

Fix it: if it is your own router

The fix is on the router, not the iPhone. Apple’s instruction is to “update the settings of your Wi-Fi router to meet or exceed the security standards” in its guide. Router menus differ by brand, but the setting is usually called Security, Security mode or Authentication, under the wireless or WiFi section of the router’s app or admin page.

1. Open your router’s app or admin page. The address and login are usually printed on a label on the router or in its manual.
2. Find the WiFi security setting for each band (2.4 GHz, 5 GHz and 6 GHz if you have it).
3. Choose WPA3 Personal. If you have older devices that can’t join WPA3, choose WPA2/WPA3 Transitional instead.
4. If neither is offered, choose WPA2 Personal (AES). Apple calls this “appropriate when you can’t use one of the more secure modes”. Avoid anything with TKIP in the name.
5. Save, then rejoin the network on your iPhone. If the warning stays, check for a router firmware update; very old routers may not offer WPA2 AES at all.

While you are there, Apple also recommends setting the radio mode to “All”, or to Wi-Fi 2 through Wi-Fi 6 or later, and not hiding the network name.

Fix it: if it is not your network

At a hotel, café, office or a friend’s place you can’t change the router. You can still use the network sensibly:

1. Tell whoever runs the network. The fix is a setting change on their router, often a five-minute job.
2. Until then, treat the connection like open public WiFi. The WiFi link adds little privacy, so you rely on each app or site’s own encryption (HTTPS).
3. Use mobile data for banking, payments and work logins, or a VPN your employer or a trusted provider gives you.
4. Stop if a site you know shows a certificate warning. On a weakly protected network that warning matters more, not less.
5. In Settings > Wi-Fi, tap the More Info button next to the network and turn off Auto-Join if you don’t plan to use it again.

On Android

Android phones don’t show Apple’s wording, but the cause and the fix are the same: the security mode the router uses. On many Android phones you can see a network’s details by going to Settings > Network & internet > Internet and tapping the settings icon next to the network; menus vary by manufacturer. If a network uses WEP, TKIP or no password, follow the same router steps above, or treat it as public WiFi if it isn’t yours.

When “weak security” is actually risky

• WEP or no password on a busy public network. The WiFi layer offers little or nothing, so anyone nearby is effectively on an open network with you.
• A lookalike name. If a network you’ve used before suddenly shows “Weak Security”, it may not be the same network. Confirm the exact name with the venue before joining again.
• Typing passwords into pages that aren’t HTTPS. Most apps and sites encrypt their own traffic, but a page without HTTPS on a weakly secured network is easy to read or alter.

CISA’s guidance is to make sure the access points you connect to use at least WPA2, and that WPA3 is currently the strongest option. SentryFi doesn’t change phone or router settings. It checks the network you are on for warning signs — an unexpected sign-in page, DNS answers that differ from trusted DNS, certificate problems, a hidden proxy — and gives a 0–100 risk score with plain next steps.