Need Help with Internet Access Breach within Home Network

[Boomwebsearch]

Today, I noticed that one of my relatives that knows my WIFI password mistakenly gave it away to someone that visited the property. This person told me that they gave out the password to someone and that they should not have access to our home network. I have a Netgear WNDR3400v1 and I do not even know what device was the one that connected and how I am to get it blocked without changing the password. Please help me with this issue that I am having before they potentially steal information from the network or something bad along those lines.

[Wh0_Am_1]

1 minute ago, Boomwebsearch said:

Today, I noticed that one of my relatives that knows my WIFI password mistakenly gave it away to someone that visited the property. This person told me that they gave out the password to someone and that they should not have access to our home network. I have a Netgear WNDR3400v1 and I do not even know what device was the one that connected and how I am to get it blocked without changing the password. Please help me with this issue that I am having before they potentially steal information from the network or something bad along those lines.

Just change the password, all the packets that are sent via your router is encrypted with the password, if they know the password and you are seriously afraid of getting hacked, then change your password, else they have access to all the data on your network no matter what they do.  

[johanneslol11]

Just apply mac filtering...  or change your password.

[Alex Atkin UK]

Changing the password is really the only secure way.  They could easily bypass MAC filtering plus you'd need to know which device it was to apply it.