Spoofing is a term used for someone faking the caller ID information that's sent when he places a call. It can be used for harmless pranks or for anonymity for innocent purposes, but it can also be used by fraudsters to impersonate someone else or to disguise a true phone number. If you suspect someone is calling you from a fake number, ask to return the call to the person or the organization he represents — at a well-known phone number. If you think a crime is being committed, consider calling the authorities.
Understanding Caller ID Spoofing
Normally when you receive a phone call on a modern cellphone or landline phone, the caller ID display will indicate the number of the person calling you and potentially the name of an associated person or business. Knowing who's calling can help you decide how to greet a caller or whether to let a particular call go to voicemail.
Unfortunately, the system for transmitting caller ID information isn't built for security, and it's possible for a caller to send fake identifying information. This can be done to anonymize a call, sometimes sending obviously fake numbers such as ones consisting of all zeros, but it can also be done as a way to deceive the person getting the call.
In some cases, people attempt to call from numbers similar to the one they're calling in order to get call recipients' attention and make it seem as though a neighbor could be calling. In other cases, they might impersonate well-known numbers such as those associated with banks, utility companies or government agencies.
Keeping Yourself Safe
Because of caller ID spoofing, it's important not to put too much trust in what your caller ID shows. If you receive a call claiming to be from an organization demanding money or your personal information, such as account numbers or Social Security numbers, be wary. Ask to call back the person on the other end of the line, and call back at a well-known, published number for that organization. Search the organization's website or look at literature you might have from the organization, such as a bill or the back of a credit or debit card, to find the best number to use.
Keep in mind that organizations like banks, police departments and the Internal Revenue Service won't call demanding immediate payment of money over the phone. Legitimate organizations will also understand your desire to keep yourself safe and won't object to your returning a call if you're not sure everything is on the up-and-up. Try not to panic if you receive an alarming call before you determine if it's in fact legitimate.
If you suspect a call is fraudulent, you can report it to your local police department or to the Federal Trade Commission. Another option is to contact your phone company for help. Many provide technology to help you block particular numbers and to filter out what appear to be scam calls. You may also be able to find apps for your smart phone to block numbers and detect likely scams.
What's a Phone Trap Line?
Toll-free numbers, such as 1-800 numbers in the United States, receive slightly different information than ordinary numbers when they receive a call. They receive additional information about the caller's number through a system called automated number identification, or ANI, since they're responsible for footing the bill for the call and must have reliable information to know their bills are correct.
Some telephone companies and investigative agencies use what's called a "phone trap line" to detect fraudulent calls by looking for discrepancies between caller ID and ANI information.