Paranoia is the best way to protect yourself from shoulder surfers

PUBLISHED : Tuesday, 04 April, 2006, 12:00am
UPDATED : Tuesday, 04 April, 2006, 12:00am

What exactly is 'shoulder surfing'? I have heard the term and I think it has something to do with looking over somebody's shoulder while they are using a computer. Is there any way to stop this? I have heard there is a type of screen available that blocks what others can see. Who makes these, what are they called and are they any good?

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Shoulder surfing usually refers to the act of surreptitiously watching what people type into a computer or ATM.

On my first trip to San Francisco 11 years ago I nearly got into a fight because I inadvertently jumped an ATM queue. There was a woman using the machine and I went and stood right behind her, just as I would have done in Hong Kong. I didn't notice a man hovering about three metres behind her until he told me to get into the queue. I then realised that Americans expect people to stand away at ATMs to prevent shoulder surfing.

There seems to be little more one can do to prevent ATM shoulder surfing - in Hong Kong or anywhere else - apart from being suspicious and observant.

When using a computer it is probably not a good idea to enter sensitive data if there is a chance that someone could observe your keystrokes. Make sure there is no one behind you or on either side. As always with matters of security, the more paranoid you are the safer you will be.

Sometimes one cannot help seeing someone else's screen. Have you ever noticed inadvertently that the person next to you on the plane is typing out a business plan or spreadsheet? Did you look away immediately?

There are ways to prevent this with something called a privacy filter or privacy screen. 3M sells them, but I have no idea how good they are. The filters work like Venetian blinds, blocking out the view from the sides but allowing you to see the screen head on. Maybe they work, but I would want to test one before buying it.

I still think the best way to protect your privacy is to be paranoid about what other people can see. I would not even open a sensitive document, let alone write one, if I knew people were sitting next to me on a train or plane.

The idea behind a gadget like a privacy filter is that you can only see it if you are looking directly at the screen. This cuts out the people in the seats next to you, but what about the person in the seat behind?

For the filter to be genuinely useful it would also have to prevent those behind you from watching your screen.

This site will give you some idea of what these screens do, should you want one: