Caller ID spoofing is a service that allows a caller to masquerade as someone else by falsifying the number that appears on the recipient's caller ID display. Just as e-mail spoofing can make it appear that a message came from any e-mail address the sender chooses, caller ID spoofing can make a call appear to come from any phone number the caller wishes
Caller ID spoofing has long been the domain of pranksters and scammers, but although the technology often is used unethically, there may be a few legitimate reasons why you would want to disguise your phone number's Caller ID, rather than just block it. Here are a few that come to mind and easy ways to masquerade as someone else.
Caller ID spoofing in general, however, isn't illegal in the US. There are scenarios where you might want to use it:
Perhaps you're working from home one day but need to place a call to a client or customer and want to appear to be working from the office—or just not give out your home or cell number (Doctors in particular may have this need). With Caller ID spoofing, you can appear to be placing the call from your office.
SpoofCard is one of the biggest and oldest, and it offers a free test drive of its service. Enter your number, the number you want to call, and the number you want to be displayed on their website widget to place the call.
With Spoofcard, users input the number they want to call, and what number they want displayed on the other end — initiating an untraceable call that leaves the other person only seeing the spoofed caller ID.
For a hacker trying to gain access to someone's online accounts, spoofing the call number is just step one in a social engineering play to convince a customer service representative they are legitimate. In the Fusion example, a hacker named John Doe spoofs her target's number and then pretends to be his wife, taking complete control over his cell phone account in a matter of minutes.