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False positives

Driving in to work this morning, I discovered a wonderful failure mode of an alerting system. My car has a weight sensor in the passenger seat; if it detects a possible passenger in the seat, without a safety belt in use, it alerts you.

Now, our other car has had this, and it's just a little red light on the dash. But this car starts an audible dinging alarm, which then goes to a very fast audible alarm. I'm not sure if it will turn itself off, as I moved my backpack quickly from the passenger seat to the floor. But what was my first thought?

Man, I've got to disable that alarm.

And that's where security systems can get it wrong. If you put in a control that annoys your end users, your end users will actively work to defeat the system. And that's when you've reduced security, because usually, their workaround is more unsafe than the pre-security system (in this case, disabling the alarm might also eliminate the red warning light, which is a tolerable false positive, but would catch an unsafe passenger).