Additional SSIDs appearing on WiFi Network

[IDHFMH]

I am trying to help an elderly friend of mine who has just moved to a new apartment.  He has taken his existing TalkTalk wifi hub with him and it is connected correctly.  However, there are two additional SSIDs which are appearing:  one with the suffix _5GEXT and the other with _2GEXT.   He does not have any wifi extenders and the router is set up with the same SSID name for both wifi channels (i.e. without the suffix).   If he attempts to connect to either of the _nEXT SSIDs it connects but there is no internet access; if he connects to the 'base' SSID everything is working correctly.

Can anyone explain what is causing this?  Is it possible that the neighbours in the apartment above him have extenders and they are repeating his SSID name?

[Debbie-TalkTalk]

Hi IDHFMH

That's great, thanks for letting us know.

Debbie

[FritzCT]

Late to the party as usual but as many including @IDHFMH seem to have realised _EXT is an extender. If your friend defo has none then it is possible the neighbours do and they have somehow jumped onto the network. Also some devices can act as a repeater so switching things on and off would be the way to go.

Rgeardless of what it is/ was I would follow @Divsec advise.

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@Divsec wrote:

Hi @IDHFMH I'd still  change my ssid, password, and router password. 

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It probably isn't necessary but worthit as a precaution.

Watching with interst to see what it was.

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[Divsec]

Hi @IDHFMH agree with @martswain if you're able to share the solution

[martswain]

@IDHFMH please let us know how it was solved, it's an interesting topic.

[IDHFMH]

All sorted now - thank you all for your help

[Michelle-TalkTalk]

Hello,

Please let us know how you get on and if you need any assistance.

Thanks

[IDHFMH]

I will check what happens to the _EXT SSIDs when I power off the router next time I pay him a visit.   

My fiend only has a Chromebook and although it says it is connected another notification says you may need to sign in...  when you open a browser window there are no such prompts.

The router is a Sagemcom FAST 5364-3

[Divsec]

Hi @IDHFMH I'd still  change my ssid, password, and router password. 

[martswain]

What happens to the mystery SSIDs when you turn off the router ?

When you connect to them are they "open" or do they require a password ?

What model router is it ?

[IDHFMH]

@Divsec Thank you for your response. Just be clear, my friend's neighbour is also on TalkTalk but with a different SSID - see attached

[Divsec]

Hi @IDHFMH Kind of you to help your chum. Try changing the said and see if the  ext follows the change. View or Change your Wi-Fi name and password . If it does change the password!

Sorry that might  mean a lot of extra but at least the leech will be denied. Also change the router password.