How online photos reveal more than you know

8 11 2010


Robert Vamosi, PC World US

The geotagging data contained in many mobile phone images can let strangers know exactly where you are and what you’ve been up to.

Digital cameras and cameraphones mean you can snap those special moments to your hearts content, preview the shot and erase and re-take if necessary.

The technology gets even better thanks to the help of social networks such as Twitter and Facebook, which let you share those special moments with your friends, family and followers around the world.

However, its worth stopping and thinking about the fact that when you post the picture on a social network, millions of web users across the globe can discover the exact location you were in when you captured the shot.

EXIF data and Geotagging

Exchangeable Image File format (EXIF) specification adds metadata to common JPG and TIFF image files. Along with a thumbnail image of the photo, EXIF data stores details about aperture, shutter speed, focal length, metering mode, and ISO settings, some of which can help a printer do a better job of colour-matching the final printed image. There’s also room for other information, such as the camera’s make, model, and registration number, and in some cases, location data.

Geotagging is the process of storing latitude and longitude data inside an image’s EXIF data. This information maps the image with a photographer’s specific geographic location, which mapping services such as Google Earth can then chart.

Many newer digital cameras and mobile phone cameras have built-in GPS receivers. The geotagging features in these newer devices are integrated and seamless. With the explosion of smartphones today, Jackson is seeing about three percent of all photos posted on Twitter contain location data, and that figure is growing.

In his New HOPE security conference presentation, Jackson detailed how he found personal details about a man in a photo. Using accompanying geotagging data, Jackson located the man’s house on Google Earth. Then he found a name associated with the house where the photo was taken, leading him to a Facebook account that yielded a birth date, marriage status, and friends. A second username listed on the Facebook page led to a second Twitter account, and so forth. The point here is that once you start pulling on the thread of information contained in a geotagged image, a single photo can reveal a whole trove of personal data.

Some people say they don’t mind sharing their real-time location data with total strangers. But others dislike the idea that strangers can know where they are at any given time. Fortunately, smartphones and cameras let you turn off the photo geotagging feature.

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