NEW YORK (CBS) ― You may consider your cell phone or smart phone a life-saver — instant communication at your fingertips. But those devices can also be used to spy on you, without you ever realizing it.

Here’s how it happens and what you can do to protect yourself.

His name is Jamie. He doesn’t want to reveal his full identity, but he wants to warn others. He said someone has used his cell phone to spy on him.

“I had no idea that this was even capable of going on,” he said.

He claims that not only were his calls being intercepted, but also that someone was listening to his conversations.

“And the only person who knew was the person I was talking to in the room without the phone being on or the phone was on but I wasn’t using the phone,” he said.

That right’s … spyware can activate your phone’s microphone and listen in to whatever is going on in a room. Jamie said it happened even during some of his most private moments.

“Some of the intimate situations in my bedroom have been heard,” he said.

He said the spy sent him text messages the next morning.

“Hope you guys had fun last night,” Jamie said.

So how do spies do it?

A spyware or malware program — sold on the Internet — can be downloaded onto your cell phone with a web browser, and a smart phone.

“Could be anybody’s cell phone,” said Eric Robi, president of computer forensics firm Elluma Discovery.

Robi said spyware can get onto your phone through an email or text message with a Trojan horse that hides the program, or through a computer connected to your phone.

“You can get someone’s text messages. You can get their emails, do GPS tracking,” Robi said.

After Robi downloaded the spyware onto his BlackBerry, he sent an email to his co-worker John.

Minutes later, that email showed up on the spyware’s webpage.

“This is the entire content of the email, so it’s pretty scary,” Robi said.

And spyware can even activate your phone’s video camera, so someone can watch and record everything you do.

So how can you protect yourself?

There are some anti-spyware programs. Robi downloaded one program that blocked the spyware from working.

“This is about $40 for this particular package,” he said.

As for Jamie, he’s changed his phone number and reported his case to police, but they say whoever spied on him is not likely to be caught.

“It’s impossible to catch this person,” he said.

It is very difficult to tell if you are being spied on. One popular spy program sends a four-letter, random text. Other clues include if you have a BlackBerry your red light may blink more frequently and your battery may wear out more rapidly than usual.

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