FAIRFIELD, N.J. (CBSNewYork) — Your Social Security number, your ATM PIN number, and even your address are all usually kept confidential — but what about your cellphone number?

As CBS2’s Tracee Carrasco reported, consumers need to keep their cellphone numbers closely guarded too – though not everyone does.

“I don’t really think twice,” one person said.

“I don’t give my number out very often,” another said.

According to the Centers for DC Disease Control and Prevention, nearly half of American homes no longer use a land line. A cellphone number is all they have.

“Your Social Security number is used to uniquely identify you,” said Ian Marlow, a cybersecurity expert and chief executive officer of Fitech LLC. “Your cellphone number is used to also do that.”

Marlow said the concern is not just ending up on a telemarketer’s list. In the wrong hands, your cell phone number can be the gateway to your private information.

“Just even a cellphone scam is someone calling you and you answer it, and the phone might even say Verizon or AT&T and they’re going to say, ‘We know your name, we know your address, we need to confirm a bunch of information for billing purposes,’ and they’ll fill in the information and begin to ask you your PIN code or Social Security number,” Marlow said, “and the moment you answer that, now you’ve really gotten yourself in trouble.”

So exactly how easy is it to get the personal information linked to your number? Using Carrasco’s personal cellphone number, the results were scary.

“So we’ve got name, address, previous addresses, other phone numbers,” Marlow said.

Using an online reverse phone number search, Marlow in minutes found all of that information plus the names, address and phone numbers of Carrasco’s family members.

“You could use the information generated from the reports to continue to dig and use other resources to generate a Social Security number,” Marlow said.

But there are ways to protect yourself.

“There’s multiple options to have another phone number. There are apps that you can download that will make your phone have a separate phone number from its number. There’s Google Voice,” Marlow said, “so you can protect yourself if you give yourself that second number.”

The lesson is that your cellphone number is much more than just 10 digits.