I received the following email from ComCast and attempted to determine what was the underlying problem:
Constant Guard Security Notice
After spending over 90 minutes on hold waiting for various agents the final resolution was "we do not know what generated this incident". I had already run a full system scan with Norton Security Suite / Constant Guard and found nothing. The Comcast Modem/Router was password protected with a 14 character password and there had been no devices except my 2 laptop, 1 desktop computers and 2 iPad devices on the network.
Any ideas from the field?
You can do all the manual scans you want but I would suggest getting a malware expert to have a look. I supplied a list of reputable websites that offer FREE malware removal assistance from a trained technician in this stickied post: https://forums.xfinity.com/t5/Anti-Virus-Software-Internet/Where-to-Seek-Malware-Removal-Assistance/...
All the websites listed are affiliated with and their volunteers receive similar training from: https://uniteagainstmalware.com/
1. You will need to create an account at the forum (takes less than a minute).
2. Download and run Farbar Recovery Scan Tool (FRST) or a similar scan tool that will produce diagnostic logs.
3. Create a new topic on the forum and post the requested logs for review.
If any malware is found, the malware removal expert will provide step-by-step instructions and guide you through each step in the removal. Peace of mind in knowing your computer is free of any bad stuff could not be easier.
P.S. You would need to do this for each connected PC or laptop. I doubt the problem lies with the iPads.