Could be that the camera is picking up traffic and attempted log in and just reporting it.
Might have the ISP give you a new IP address on the modem and see what happens.
Most cable internet providers use DHCP to give out IPs. The IPs aren't assigned, so they can't give "new" ones out. The usual procedure is to change the WAN MAC address of the router and reboot the modem. This will cause the modem to think it is a new device and will be forced to assign a new IP.
To change the MAC of the router (assuming you have a EA4500) is Connectivity > Internet Settings > MAC address clone as seen in
this emulator.