You picked up something on your internet travels. I hope you have a anti-virus (McAfee, Norton, whatever) on board and clean your computer - CCleaner is free and good - of the junk every once in awhile. Also Malwarebytes - also free - run occasionally helps. Of course you are behind the built-in firewall that Windows offers in its program. Also, you should have Ad-Block on Internet Explorer but some people don't like it, but I've never had a problem with it.

Regardless, for that message to pop up, I doubt very much if it has ANYTHING to do with Mediacom, it is something else you have on your registry now that will continue to pop up now that it has your IP address.

Clean that computer.

This could possibly be a 'ransomware' infection. Some of these are able to protect themselves from normal malware scans.

To eradicate it for good;

1. Grab a new or newly formatted usb drive and install the portable version of Malwarebytes or SuperAntiSpyware on it.
2. Boot your computer into Safe Mode: usually done by tapping the F8 key at boot but may vary according to machine.
3. Run the malware scan while in safe mode. Delete any quarantined items.