If you receive the "Apple Security Center" popup message below, please do not call the fake contact support telephone number in it. This is because the number is being used by scammers operating call centers. The scam aims to frighten and trick potential victims into calling the scammers, who will pretend to be from Apple.
The Apple Security Center Scam

The scammers will then attempt to deceive their potential victims into disclosing their account credentials, personal and financial information, which they will use fraudulently.
Potential victims may also be asked to give the scammers remote access to their computers, something Microsoft will never ask their users to do.
If you were tricked into disclosing your financial information, please contact your bank for help. If you were tricked into disclosing your account credentials, please change your passwords.