How many people have access to your desk when you're not around?
I assume that your co-workers are basically good people. If they weren't, you wouldn't have hired them in the first place. Does that mean you know everything about them? Or would you be like so many on the news commenting after the fact that he/she "seemed like such a nice person"? It would be a wonderful world if we could trust every person we met. Unfortunately, even good people can fall prey to temptation.
You also need to worry about the people you didn't hire. If you're like most small offices, the landlord's cleaning staff, contractors, visitors and many other outsiders have some degree of access to your space. And you generally have few assurances about who they are, what background checks were run or what supervision they receive.
You have to assume that people you can't know have access to your space when you're not around. Most of them are good people. Do what you can to help those honest people stay honest.
- Always turn off your computer at night. Don't just lock the screen. If your IT team has set it up properly, extra protections will kick in when you shut the computer all the way down.
- If you have a laptop, lock up it in a desk drawer at night. Laptops, PDAs and mobile phones are high-theft devices. Don't make it easy for the thief.
- If you have enough space, put away your paper files at night. Lock them in a desk drawer or filing cabinet. Even if the cabinet doesn't lock, it will at least be more obvious when an unauthorized person is snooping though the files. It's harder to tell when someone is snooping through the papers on top of your desk as they are "cleaning" it.
- If you can't lock the papers up, at least put a cover sheet or blank page on the top of the pile to protect the confidential information from casual oversight.
- Make sure you collect papers off faxes and printers as soon as possible. Don't leave them exposed to guests and others walking the halls.
- If you see something suspicious, call for help. If you have an internal security team, make sure everyone in the office knows how to contact them both during and after normal business hours. If your office's immediate action drill is "call the police", make sure they know how to do that, too.