How do I protect my system from cyberhacking and identity theft?

Don't give anyone the password to your account for any financial information. To start fresh change every password you have for your Apple Account and all Social Media sites and don't reuse any of those passwords. This happens all the time through phishing emails/messages from people that claim to be legitimate and asking for your information. Simply don't respond at all to any email/message by calling a phone number or clicking a link where they may want you to sign in with a password. Here is a Support Article that may help you recognize those messages:

Recognize and avoid social engineering schemes including phishing messages, phony support calls, and other scams - Apple Support

You will see emails/messages that say a charge had just occurred and want you to call a number or others that say you have a virus and they are all scams.