Is your voicemail protected?

HOUSTON (KTRK) -- There is a warning for cell phone users that may have sensitive information on their voicemails.

Hackers and curious individuals could remotely listen in without your knowledge, even if you think your voicemail is protected.

"I think everyone just assumes it's protected. You have your phone. It's your private voicemail password. You have a password to get into it," said Kristen Maurer.

But Eyewitness News showed Maurer her voicemail was unlocked and could have easily been hacked.

IT expert and private investigator Colman Ryan says it's not just Maurer's voicemail that is vulnerable. Millions of cell users could be affected as well.

"Seventy-five percent of the numbers that I've tested, I was able to get into," Ryan said.

Hackers are accessing voicemails through a number that most cell phone users are unaware of.

"The backdoor voicemail number. And by having that, you can check the voicemail without ever ringing the phone," Ryan said.

If users only check their messages through your phone, you are accessing a virtual voicemail box without dialing in. However, the backdoor number might not be password protected, and anyone who knows that phone number can get in and have full access.

"They can delete messages. They can forward messages. They can change your greeting," Ryan said.

The hacker could also change your password and lock you out. It might not just be long-distance hackers attempting to listen to your messages. People you know might have an interest as well.

"People in divorce situations, child custody situations, ex-boyfriends, girlfriend situations. Those are the people that are figuring out how to get into the voicemail," Ryan said.

Protecting your voicemail is quite simple, according to Ryan.

"It has to do with an option set on the back end, on the voicemail system. Go into your voicemail, go into your options, and setting the option to the pin number to be entered when checking the voicemail," Ryan said.

Ryan says this is different from accessing the virtual voicemail through your smart phone. You actually have to call in and go through the command prompts to enable password protection. This varies based on your cell carrier, so be sure to check with your provider on how to access the voicemail system from your phone.

The biggest red flag that a voicemail has been hacked is noticing that a call was missed from your own number. If you notice this on your smart phone, you should immediately check your voicemail settings and make sure it's the password is enabled and change it if you think you've been compromised.

Also, experts advise to use a six or eight digit pin rather than four digits to increase security.