A cautionary tale, excerpted from...
Chained Exploits: Advanced Hacking Attacks from Start to Finish
"Phoenix knows that Mr. Minutia has been spying on him for some time now. Phoenix sees Mr. Minutia at his desk, shuffling through papers, whenever he leaves his desk to go to the copy machine. Phoenix notices Mr. Minutia walk over to his desk whenever he is on the phone to eavesdrop on his conversations. Now Mr. Minutia has taken it to the next step by reading all of Phoenix’s e-mails and reviewing the Web sites Phoenix views.
The word hypocrite echoes in Phoenix’s mind. He knows his boss spends the majority of his time at work surfing the Internet. Phoenix is not sure what his boss is looking at, but Phoenix is determined to find out because he suspects it might not be work related. Then Phoenix can approach Mr. Minutia with a taste of his own medicine and expose his Internet-surfing habits. Phoenix begins to plot how he is going to spy on his boss." (more)
Make sure your employees are not spying on you.
Hey, there are textbooks writing about this.
Inspect for electronic surveillance regularly.