But stop and think about the implications. A computer intruder can call you at home claiming to be from the IT department at your company. The person on the line urgently needs your password to restore your files from a server crash. Or the caller ID displays the name and number of your bank or stock brokerage house, the pretty sounding girl just needs to verify your account numbers and your mother's maiden name. For good measure, she also needs to verify your ATM PIN because of some system problem. A stock market boiler-room operation can make their calls seem to come from Merrill Lynch or Citibank. Someone out to steal your identity could call, apparently from Visa, and convince you to tell him your Visa card number. A guy with a grudge could call and claim to be from the IRS or the FBI.