UW Computer Security Research and Course Blog

Summary

Most people have probably heard a car alarm go off sometime in their life, and the chances are that it was a false positive are also pretty good. Usually cars that have an alarm have some sort of alarm in place will try to advertise this fact, such as having a small blinking red light to indicate that there is some sort of security in place. Car alarms can trigger on a variety of events. Some of these triggers are vibrations, rotations, contact, pulling of a handle, changes in battery voltage, and sound. When triggered, the car will emit some sort of loud, repetitive, obnoxious sound for many minutes, or until it is turned off using some sort of authentication, usually the clicker of the car. The general idea is that sound attracts attention, so if some set of illegitimate events are happening to someone’s car, other might notice and come to the rescue. One of the most likely people to react to the sound of a car alarm is the owner. However if someone breaks a car’s window, the alarm goes off, and then they run away, the owner still loses. So the alarm really is more of a deterrent than a real physical barrier.

Assets

• The owner of the car wants their car and all of their belongings inside the car to remain undamaged and stolen. There is a very real monetary value that these physical possessions have.
• The hearing of any individuals inside or the car when the alarm goes off. If an owner accidentally triggers the alarm, and they are right next to the car, it would be bad if the alarm damaged their hearing. This is probably even true for burglars, if they go deaf from an alarm, they probably could sue the manufacture (on in America! =p ).
• People a usually trying to sleep during the night. If a car alarm goes off in the night, people might wake up and be unhappy. This is another limit on the loudness and duration of the alarm.
• The interest random pedestrians have in car alarms needs to be fairly high. If the car alarm that cried wolf goes off everyday accidentally, if one day it goes off legitimately, it if fairly likely that no one will do anything.

Advesaries

• Thieves are probably the biggest adversary. They want to steal your stuff. You don’t want them to. Regardless of if they want to steal your car, your airbags, or your laptop you left in the backseat, they probably have to get past your car alarm. Some of these people are probably fairly experienced in this field, and they might have specialized tools for opening cars.
• Some people might find it fun or enjoyable to set off car alarms, even if they are not going to steal anything.

Weaknesses

• Car alarms don’t actually stop the adversary from doing anything. So if they are fast enough, or in a remote enough location so that there are no people around, they might be able to avoid any other people, even if they do come as soon as they hear the alarm.
• Someone could go around a neighborhood every night for a series of days, purposefully triggering every car alarm they could find. People would probably stop caring very much every time an alarm went off if it became a very routine thing. Once this happens, it might be easier to take stuff or steal the car.
• Alarms have to be powered by something, so if someone could disconnect the battery from the alarm before they did something that the alarm would trigger from, they would avoid any problems.
• If an alarm is too hard to trigger, like if only goes off when a door is opened, but the window can be broken instead, then it can be circumvented.

Defenses

• An alarm could be tweaked to be easier/harder and softer/louder to try to find some equilibrium where enough attention is attracted, and not too much damage is done by the sound.
• The sounds are usually made to be fairly hard to ignore. Alarms that employ a series of different sounds that are all fairly abrasive make it difficult to zone the sound out.
• Car alarms could do more than just make noise, such as stop the engine from starting.

Risks and Conclusion

Not everyone needs the kind of security an alarm provides. A car that barely runs in Montana, or a school bus, probably do not need alarms. Likewise, a brand new Porsche in the middle of bad neighborhood probably needs more security than just an alarm. And there are many other security measures out there. Such as wheel locks, remote immobilizers, vehicle tracking, indoor/gated parking garages, security guards, ect. In the end, car alarms are really just one layer of defense against theft, and ultimately the owner will have to decide how much security they think they need to keep their stuff safe.