To avoid being scammed via computer:
One and only rule: Don't even download, install, click a link or give any sort of remote access to a stranger. Operating systems are pretty secure nowadays especially behind routers (so the IP is not directly pointing to a physical computer).
A basic firewall and anti-virus is all you need. What these criminals try to do is convince you to bypass the already secure PC which you help them to do out of fear.
If you feel yourself being convinced, ask them to hold while you call the official number to inquire about the caller. I'm pretty sure they'll hang up.
This cannot be undone and I am sure it will be greatly appreciated.
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