A Wall Street Journal investigation of 101 smartphone applications found that more than half of them transmit personal data to outside providers -- especially to advertisers.

56 of those 101 apps sent users' unique device ID to third parties and 47 of them also sent the phone's geo-location. Pandora and TextPlus 4 apps were found to submit age, gender, location and phone identifiers to as many as eight ad companies.

How can you stop this from happening and protect your privacy?

Step 1: Turn off your smartphone.

Step 2: Throw it on the ground.

Step 3: Jump on it repeatedly.

Sadly, that may be the only way. "In the world of mobile, there is no anonymity," Michael Becker of the Mobile Marketing Association told WSJ.

Meghan O'Holleran of Traffic Marketplace, an Internet ad network, said "The great thing about mobile is you can't clear a Unique Device ID like you can a cookie [on your computer]. We watch what apps you download, how frequently you use them [and] how much time you spend on them."

Both Google and Apple, who make the Android and the iPhone, allow advertisers to target users but claim they don't track individuals based on the way they use apps, according to WSJ. Both companies claim the responsibility is on the app makers and the users who download them.

All kidding aside, here's what you can really do:

1. Turn off your phone's location tracker (on the iPhone, it's under Settings -> General -> Location Services... on the Android, go to Maps -> Latitude -> Privacy). This will prevent some location-based apps like AroundMe, Foursquare or Moviefone from being useful, but it will at least stop apps from transmitting where you are.

2. Some apps have opt-out features that will stop them from sending information to targeted advertisers, but most don't. However, some advertisers will let you opt out by emailing them directly. According to WSJ, ad company Jumptap Inc. will let you email your Unique Device ID (a.k.a. the serial number) to optout@jumptap.com. Apple won't turn off ads, but you can stop personal data from being sent to their iAd system at http://oo.apple.com. Google offers less help, claiming they don't create user profiles -- the apps do.

3. Don't use the apps. It'll somewhat defeat the purpose of having a smartphone, but if you're not downloading or using a game app, how will it know to tell ad companies that you like to play Zombie Duck Hunt while sitting in a Starbucks? It won't.

How do I know what info is being sent?

In September, researchers from Intel, Duke University and Penn State developed a real-time privacy monitoring application called TaintDroid. The app alerts users when data is being sent to outside sources and, according to Fast Company, two out of three apps misuse personal information solely for targeted advertisers.

Unfortunately, the app only works for Google's Android phones and requires "jailbreaking" since it has not been approved it for use. ("Jailbreaking" is the term used to override Android and iPhone security settings to install unapproved apps, and voids the warranty in your contract.) Worse yet, TaintDroid doesn't actually stop your personal data from being transmitted, it just tells you what's being sent.

Ultimately, you might just have to accept that all the privileges and perks that come with a smartphone also comes with a small sacrifice of security. Some personal info will be put out there whether you like it or not, but some solutions are simple. For example, if you don't want a nude photo of yourself to end up on the internet, then keep your clothes on when you're taking pictures.

In other words, be smart with your smartphones out there.