Nearly all cell phones, digital cameras, and scanners insert metadata in the digital photos they capture. This is done using the Exchangeable image file format (Exif) data structure or standard.
Some devices just embed the make and model of the camera. Other devices insert more extensive data such as camera settings, GPS location data, and other information that might be specific to that camera or cell phone. Many owners of digital cameras and cell phones are oblivious that their photos are tagged with sensitive information.
Since the Exif data contain information about the photo, the Exif data pose privacy and security concerns. When pictures from these devices are posted online, the Exif metadata can be used to sense the time the photo was taken and the location where it was taken, if the camera or cell phone has the GPS location data feature. The distinctive ID number of the camera device can be used to identify the owner of the camera. It is therefore best to remove Exif data before publishing or posting pictures online and avoid privacy and security concerns.
My favorite software to remove Exif data is ExifTool by Phil Harvey. Exiftool is a cross-platform tool that can remove, modify, and add Exif and other metadata in various file formats. The software is intuitive and easy to use. I use the command line to manipulate whole directories of files using a combination of command options and wildcards.
exiftool.exe -all= -overwrite_original *.jpg