So sorry! Wish it was not true!

It's not easy, you can pay to use a service such as DigiMarc http://www.digimarc.com/digimarc-for-images/professional-edition but you also need Adobe Photoshop to use it or you can try to track them manually using http://www.tineye.com However, if they can be seen on screen then nothing you do can stop someone "stealing" them, unless you practically obliterate the images with watermarks. However, if someone does "steal" them, you can use the sites contact details to ask they be removed. If they won't or don't, then you can file a DMCA http://d.pr/oCt2 However, it's often a lot of time and wasted effort to keep chasing an ever-expanding group of people, especially if someone uploads them to somewhere like PhotoBucket or Flickr where they get marked public domain and hundreds of other people innocently start downloading them and reusing. Sorry! Rich.