I encourage my students to go over and visit Rick, Paul and Bill’s blog. In 2009, Rick posted a link to a Scientific American article on How Hackers Steal Secrets from Reflections. Great Article. With our students going through some of the best security courses available, these links are very valuable.
Although we used a mirror for this example, we have tried glasses and other reflective materials and you can take a picture and reverse the photo.
Reversed with Irfanview