You changed the WiFi password — what to check next

Eleven at night. Your phone shows a device on the network that nobody in the house recognises. You open the router page, type a new WiFi password, save, and the house spends twenty minutes reconnecting everything. Peace.

Except the password is only one of four locks on that door, and it is the easiest one to change. The other three are usually still on factory settings — which is exactly how the unfamiliar device got in.

What a new password actually does

It changes the key to the WiFi. Any device that was joined has to prove it knows the new key, and it does not, so it is dropped and cannot rejoin.

That is real, and it is worth doing. But it settles one question — can that device get on the WiFi — and leaves three others open:

A device on a cable is untouched. Its traffic never passes the WiFi login at all.
A second router or extender still holding the old key keeps running its own network with its own name. The intruder may have been on that one, not yours.
The router's own admin login is a different password entirely. If someone was on your network, they could reach the router page and change settings there. A new WiFi password does not touch any of it.

So the useful question after changing the password is not "am I safe now". It is "how do I check".

The check: count your own devices, then look at the router's list

This takes about two minutes and needs no tools beyond the router page.

On a phone or laptop, write down every device in the house that uses the internet — phones, laptops, the TV, the console, the printer, the CCTV box, smart plugs. Be honest and be thorough; the plug behind the sofa counts.
Open the router admin page. The address is usually on a sticker under the router, and so is the login. Look for a menu called Attached Devices, Connected Devices, DHCP Client List or Network Map.
Count what the router shows, and compare with your list. Names are often unhelpful — android-9f2c tells you nothing — so go by the total first.
Write the total down. Look again tomorrow at the same time.

Two numbers tell you a lot. Router count higher than your list by one or two, and staying higher a day later: something is still joined. Count matching exactly, both times: whatever it was, it is not on the WiFi any more.

Do not skip the second look. Some devices reconnect slowly, and some come back because a housemate quietly gave out the new password.

The four settings worth checking while you are in there

What	Where it lives	What you want
WiFi password	Wireless / WiFi settings	New one, WPA2 or WPA3, not the old name plus `123`
Router admin password	System, Administration, or Maintenance	Changed from factory. `admin`/`admin` is an open door
WPS	Wireless, often its own tab	Off
Port forwarding / virtual server	NAT, Forwarding, or Advanced	Empty, unless you set a rule yourself
Remote management, DDNS	Administration, Remote Access	Off, unless you use it on purpose
Guest network	Guest WiFi	Separate password, still on — this is the one for visitors

That WPS row is the one people skip. It exists so you can join without typing a password, and it is the softest way onto a network that still has it switched on. If you never use it, turn it off and leave it off.

The guest network row is the polite fix for the actual problem. Visitors, the delivery rider charging a phone, the cousin staying two nights — they all go on the guest network, which you can switch off entirely when they leave. Your main password then stays in the family.

The cause nobody mentions: the router's own settings

Here is the part that a new WiFi password genuinely cannot fix, and it is the reason this article exists.

If someone was on your network long enough to be noticed, they could open the router page. On a router still using the factory admin login — which is more common than people assume, because the ISP technician sets it up and nobody touches it again — they can:

add a port forwarding rule that lets them reach a device inside your house from outside,
switch on DDNS or remote management, which does the same thing more conveniently,
change the DNS servers, so your browsing is answered by a machine of their choosing,
turn off the WiFi schedule or parental controls you had set.

None of these disappear when you change the WiFi password, because none of them are guarded by it. They live behind the admin login, and that login is usually still the sticker.

So the order of work is: new WiFi password, then new admin password, then clear any forwarding or remote access rule you did not create yourself, then check the DNS setting says what you expect. On many ISP routers this last part needs the provider — see the FAQ above.

What to do, cheapest first

Free, five minutes: the device count above, WPS off, admin password changed, guest network switched on for visitors. That closes the doors that were actually open.

Free, and worth knowing: MAC filtering and a hidden network name are not security. They are commonly recommended, commonly used by attackers' tools without trouble, and they break your own devices at the worst moment. Skip them unless you enjoy reconnecting printers.

Then hardware. If the router is old enough that the admin page offers none of the settings above — no client list, no WPS switch, no forwarding tab — you cannot check anything, and that is the real argument for a router you control yourself. A router you can see into is worth more than a faster plan you cannot.

Then, and only then, the plan. Nothing about an intruder is fixed by more speed. If the WiFi also feels slow, that is a separate problem with a separate test — start there, not with the password.

After the doors are shut

Two small habits make the next time easier. Give the guest network its own name, so you can tell at a glance which one a device is on. And once a month, open the client list for thirty seconds and count — the same way you would glance at a bank statement. Unfamiliar device, and now you have the settings already in hand to deal with it.

One thing this guide will not do is tell you how to see what that device was doing. Network logs on home routers are thin, usually limited to which addresses were contacted and when, and reading them properly is a job for someone with the router in front of them.

Quick answers

Does changing the WiFi password kick the person off straight away?

Off the WiFi, yes. Their phone or laptop can no longer complete the login, so it drops and cannot rejoin unless they are told the new password. Two exceptions people miss: anything plugged into the router with a cable is completely unaffected, and a second router or extender that still holds the old password can keep broadcasting a network of its own. That is why the client list check below matters more than the password itself.

Is hiding the network name or filtering MAC addresses worth doing?

Not as protection. A hidden name is still visible to anyone scanning properly, so it mostly causes your own devices to fail to reconnect. MAC filtering is beaten by cloning the address of a device that is already allowed. Both feel like security and behave like inconvenience. A strong password and WPA2 or WPA3 do the real work.

Should I change my bank and email passwords too?

Changing a WiFi password and changing an account password solve different things. A WiFi password controls who can use your line, not who can log into your accounts. Change account passwords if you have a real reason to think someone had access to a device of yours, and do it through the app or website itself, with two-step verification on. Do not act on a message from someone who contacted you about it.

My router admin page will not let me in at all. What now?

Many ISP-supplied routers lock the admin page or hand it to the provider's app. That is not a fault, and there is no safe way around it from outside. Contact your provider's support channel and ask them to turn off WPS, check for port forwarding rules you did not create, and change the admin password. We cannot do any of that for you because we do not have access to your account or line.