When I looked through the logs, I can see some lines saying “TCP connection established from x.x.x.x address” but nothing else after or other comments. Does this mean someone looged into the router somehow knowing the username & password? Or this is just someone trying to log in from outside and no success?
These are connections to a service on your router. If you don’t recognize them, your router might be compromised and running backdoor PPTP services, web proxy, SOCKS, etc.