Sharing your location with friends is easier than ever these days, but many people are unwittingly telling the world where they are every time they take a picture.
Apps like Foursquare and Urbanspoon put your current location to good use by finding things around you. And in maps programs, you can find and share locations and directions easily. But if you're not careful, your location data will be sent out in ways you're not aware of. Most modern phone cameras, for instance, will "geotag" photos you take, embedding your GPS position in the image's EXIF metadata -- where things like date and exposure information go.
This can be great for, say, tourists who can see their photos on a map without having to tag them individually. And even around town, it can be nice to have a reminder of where the restaurant was where you took a picture of your friends around the table.
But like most conveniences in tech, there's a dark side. Just a week ago, a hacker broke into several law enforcement databases, leaving behind a photo calling card of a woman holding a taunting message written on a piece of paper. Unfortunately, the hacker didn't think to remove the photo's GPS data, and the FBI could determine the place the photo was taken almost instantly with almost no other clues. After a little more work, they had the hacker's name and address, and arrested him without delay.
And what police can do, hackers and criminals can usually do as well. This time, the photo was back-tracked in the interests of justice, but that doesn't mean others won't use it to determine when you're out of the house or where you're meeting with friends.
Your phone and a number of services on the Internet default to using and showing your images' location data. You can usually change this, and if you can't, it's probably not a good idea to be using that service. Being aware of what data you are broadcasting on the Internet is essential for safety, so check your phone and the sites you use to share your data with friends, just to be sure.
The EFF has some more information on this, and a few useful links as well if you're looking to see how you might prevent your own data from being improperly publicized.
Devin Coldewey is a contributing writer for msnbc.com. His personal website is coldewey.cc .