My dad recently downloaded McAfee (paid version) as internet protection. However since doing so it has been alerting that there is a unknown device accessing the network. McAfee allows you to look at all computers and devices in the network so I have recorded all the known devices IP addresses and labeled them on the McAfee network defense however there are two IP addresses that are not accounted for. I marked them as intruder so now it sends alerts whenever the unknown IP address uses the network. It does not allow me to block them from using the network though but only block them from gaining access to this PC. It says the intruders using the network right now but as i've noticed McAfee is not very accurate as it also says other devices such as PS3 are using the network but are not even turned on.
I have reset the password for the router but the intruder device immediately gained access again, i've also tried to set the router so that it will only allow for the IP for the PC to accesses it but that hasn't worked either, though that could be because I did not do it correctly. I do not know what the intruder device is or how to stop it using the network, could anyone share any insight into the situation?