Are you on Facebook? Do you have a smartphone? Ever send text messages? How about emails? If you answered yes to any of those questions — and who among us would not — your life is an open book. And it doesn't really matter how careful you are about all those privacy settings.

"They used to say Big Brother is watching, but it's not just Big Brother, it's sister, mother, father, friends, co-worker, boss," said Darrin Giglio, chief investigator at North American Investigations in New York.

That makes the scheme that Fox Lake, Illinois, Police Lt. Joseph Gliniewicz managed to pull off all the more astounding. For nearly a decade, the small-town cop essentially led a double life. The charade was so convincing, it continued even beyond Gliniewicz's violent death in 2015. The story is the focus of the latest episode of "American Greed."

Known as "G.I. Joe" in the close-knit community 50 miles north of Chicago, Gliniewicz seemingly lived up to his nickname.

"He was a cop's cop," said Lee Filas, a reporter for the Daily Herald. "He was just this larger than life, 'I am the great American hero' cop, and he portrayed it every day."

But all the while, Gliniewicz was embezzling money from the local youth group he led. He even at one point contemplated hiring a hit man to cover up his crimes. The fact that he managed to keep it secret for so long, in the digital age, is a testament to his skills, says Giglio.

"Everything in your life, there's information attached. So if you have a job, there's records. You have a house or property, there's records. You have a mobile phone, there's records," he said. "We're a record-driven society."

If you want your life to be a little less conspicuous (we will give you the benefit of the doubt that you just want some more privacy and are not trying to lead a G.I. Joe-style double life), here are some of the more common mistakes people make, and why the job of a private eye, like Giglio, is a little easier than it once was.

Know your friends

When you open a Facebook account, you automatically surrender a certain amount of privacy. There is really no way around it. So one way to be more obscure is to not have an account in the first place. Of course, for most of us, that ship sailed long ago.

"You can go and delete those accounts, but usually there's records and old archive stuff that people can go through and still find information," Giglio said.

Plus, even if you don't have an account, chances are your family or friends do. A smart investigator can use that information to track you down.

If you do have an account, limit the information you share. Do you really want the world to know where you work? Your phone number? The names and locations of your family members? If the answer is no, leave it out of your profile.

"I can't even tell you the amount of cases we've solved, and information we've gotten that helps with cases from social media," Giglio said. "And people don't really realize the goods that they're giving up until after it's too late."

Also, don't accept a friend request from someone you don't know. And even if it is someone you do know, make sure you are not already friends. You could be falling for a common private investigator's trick, which crooks use as well.

"We have undercover Facebook profiles that look real," Giglio said. "And we're able to then kind of use that as a fake person to gather information on something during an investigation."

Guard your information

It is hard to avoid having some identifying information. You live at a physical address, you have a phone number and, if you are a U.S. citizen, you have a Social Security number. A determined investigator is probably going to be able find that information no matter what, but you don't need to give them any extra help.

"One person has one fingerprint. It's kind of the same with your Social Security number," Giglio said.

There are very few situations anymore in which you are required to provide your Social Security number. Don't give it out unless you absolutely must, and then keep in mind that you are giving away a total key to your identity.

You have heard again and again about securing your passwords, and hopefully you no longer access any accounts by typing "password," or "12345," or "letmein." But what about your user name or your email address?

"There's people that have their email addresses, they'll have, you know, janesmith072173," Giglio said. "So now I have a person's name and their date of birth just from their email address."

Consider changing your email address to something less obvious. There is no law that says your user name has to include your actual name. At the very least, consider removing those identifying numbers like your birth date or ZIP code.

Also, don't be a virtual pack rat. Delete old emails and text messages. That way, you will reduce your digital footprint.

Take a hard look at your hardware

Your computer or smartphone can be a treasure chest for someone looking to track you down, so don't leave them the keys.

Don't let the devices out of your sight, and make sure they are secure.

"You don't want to leave anything un-password protected, especially your phones and stuff like that because phones are lost very easily," Giglio said. "Just like you would secure your home with an alarm system and cameras and all that, you have to do that with the same diligence with your computer and your smartphone."

Always make sure your firewalls and security software are up to date, and make sure your equipment has the most current operating system. Those updates that pop up from time to time often include fixes for security bugs. Don't put off installing them.

And when you trade up to the newest model, Giglio says to be sure you have completely erased all of your information on the old device.

"People just think you're hitting the trash button, the delete button, that leaves the computer. That's just not the case."

Smile! You're on candid camera!

Anytime you leave your house, chances are you come into the view of multiple cameras. Security cameras watch our streets. Cameras with license plate readers patrol our roads. There are cameras where you least expect them. Be conscious of them, and anything you do in public.

"Used to be, just big businesses had surveillance systems. Now, everyone's house is starting to have them and the technology of those cameras, the clarity, the HD, is becoming great," Giglio said.

To escape the long arm of the surveillance state, "You'd have to go to the mountains and live in a cabin," Giglio said.

"You know, if you have nothing in your name, you're not in contact with any of your friends or family, you know, could it be done? Yeah. It's a very difficult life, and it's probably a very disciplined life."

Joe Gliniewicz was nothing if not disciplined. Even the sneakiest sneaks slip up eventually though, and G.I. Joe was no exception. But Joe was so good, his double life continued even after he died.

See how G.I. Joe managed to fool everyone for so long, and how the truth finally came out, on an all-new "American Greed," — Monday, Feb. 6 at 10 p.m. ET/PT only on CNBC.