Doing a little searching on this message "EXPLOIT Netcore Router Backdoor Access" I am seeing a lot of reports of issues with the router.
Have you contacted the manufacturer? There may be a firmware update that is needed to correct the issue. Perhaps there is a forum that they have as well. This may be something that is in discussion there.
Spectrum-Social Media Customer Care
Lead Moderator-Community Forums
This is most likely a "false positive detection" in the your TrendMicro anti-virus and firewall application software. The CMTS verifies your modem's MAC address every time it renews the DHCP lease or tries to send an update to the modem. You might need to open up the firewall so your modem CAN receive the updates being sent to it by Spectrum.