We are receiving calls from 1-800 number stating they are Apple Support and notifying us of break in iCloud security. Most likely a hoax. However, how do we check that we have not been compromised?
PowerBook
It is definitely a scam. Apple doesn't make unsolicited phone calls. If there was a problem you would be notified when attempting to log in, including when logging into this forum. Also see: Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support
Also, the caller id number shown on scam and marketing calls is rarely the number actually originating the call. The number is usually spoofed.
If it was me, I would just ignore the calls and not worry about. They are common. However if you responded and gave out your information, see: If you think your Apple ID has been compromised - Apple Support
To stop the calls, one option to consider is Settings > Phone > Silence Unknown Callers. See: Detect and block spam phone calls - Apple Support
How to check iCloud security after 1-800 "hoax" call
