Imagine someone watching your every move, hearing everything you say and knowing where you are at every moment. If you have a cell phone, it could happen to you. After four months of harassing phone calls, Courtney Kuykendall was afraid to answer her cell phone. The Tacoma, Washington, teenager was receiving graphic, violent threats at all hours. And when she and her family changed their cell phone numbers and got new phones, the calls continued. Using deep scratchy voices, anonymous stalkers literally took control of the Kuykendall's cell phones, repeatedly threatened Courtney with murder and rape, and began following the family's every move. They're listening to us and recording us," Courtney's mother, Heather Kuykendall, told NBC's Today Show. "We know that because they will record us and play it back as a voicemail." How is something like this possible? Just take a look on the internet. That's where you'll find the latest spy technology for cell phones. Spyware marketers claim you can tap into someone's calls, read their text messages and track their movements "anywhere, anytime." Security experts say it's no internet hoax."It's real, and it is pretty creepy," said Rick Mislan, a former military intelligence officer who now teaches cyber forensics at Purdue University's Department of Computer and Information Technology. Mislan has examined thousands of cell phones inside Purdue's Cyber Forensics Lab, and he says spy software can now make even the most high-tech cell phone vulnerable. "I think a lot of people think their cell phone calls are very secure but our privacy isn't always what we think it is."