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D.I.Y. Home Security
theodp writes "The NYTimes reports that pre-wired home security installations by alarm companies are on the way out. Thanks to wireless window and door sensors and motion detectors, installing and maintaining one's own security system is becoming a do-it-yourself project, with kits available from companies like InGrid and LaserShield. Time to start cranking out some new iPhone and Android apps, kids?"
Having used to work installing alarms systems, jamming wouldn't work. A lost communication with a device triggers a fault same as if you were to cut a wire. Spoofing also wouldn't work because if more than one identical ID/Serial#s also create a fault.
But yes I suppose you could keep randomly jamming them and setting off alarms until they finally give up and disable it.
I say don't drink and drive, you might spill your drink. Before you get behind the wheel just stop and think.
Try http://www.zoneminder.com/ which hits everything you mentioned. (If the webcam is Linux supported)
Wireless = a burglar could disable them remotely? ;).?br>
Either by jamming or by spoofing.
Or trigger them often enough remotely so that they eventually get disabled
I used to design radio-based alarm systems in the 1980s. These were the first things we'd make sure couldn't easily happen. In those days we only had one narrow-band channel to work with (allowed by law) so anti-jamming was basically a case of a loss of signal from the sensors and/or a blocking signal present at the receiver would trigger an alarm, which meant that (3) was a definite possibility. The 'loss of signal' detection implies that the sensors transmit continuously - they don't, but they do send a brief 'check-in' at periodic intervals. The check-in period was a pseudo-random sequence to prevent different sensors checking-in on top of each other (since they couldn't 'listen out') and as a result the receiver could very quickly determine whether a sensor had missed its checkin. Later spread-spectrum techniques got around most kinds of dumb jamming attempts - it would still be possible to spoof the system in theory but only using relatively sophisticated bogus transmissions. And spoofing is reasonably easy to prevent in the decode software. I assume most modern systems today will use much better techniques than we had at our disposal twenty years ago.
I'd say this though, as a former alarm engineer - if you really have something to protect, the best security is physical, not an alarm. If you can't secure your own building go to someone who can, e.g. safe deposit boxes. Alarms are pants, whether they use wireless or not.
AFAIK, in most localities an automated system is not permitted to call 911 directly. You're better off having a cheap prepaid cell phone call your cell phone so you can then call the police / fire.
But you'd better have a lot of confidence in your alarm system. Most municipalities will charge you for the first few false alarms, and will then either force you to remove the system or charge you with a public nuisance misdemeanor.
John
Much of this discussion has been about the jammability of RF-based alarm systems.
I've done it (testing my own system). It's NOT hard.
All the wireless sensors have a lithium battery that lasts for a few years. The sensors do NOT transmit continually- that would run down the battery in a matter of hours not years.
Each time they transmit anything, it's in the form of a data packet including headers, the transmitter's unique ID, battery status, what it wants to report (open/closed/etc) and a few checksum bits. Furthermore all the wireless sensors (generally) use the same channel in the 433MHz range. To avoid stepping on each other, each packet is transmitted a few times separated by a pseudorandom delay. The sensors also transmit a 'tamper' signal if the sensor casing is opened or ripped off the wall, and a periodic 'superivision' message once every hour or so to let the system know they're still alive.
Whenever you open or close a door connected to a wireless sensor, it transmits a burst updating its status. If it transmits an 'open' signal when the alarm is armed, the alarm goes off. If the alarm doesn't hear a supervision packet from a sensor for more than an hour or two, it signals a trouble condition.
Most importantly- the transmission is ONE WAY- the sensors don't have receivers. The sensor doesn't wait for an acknowledgment from the alarm that its packet was received-- it sends its packet a few times and then considers it sent.
Since many devices (including non-alarm stuff like wireless thermometers and other brands of alarm gear) use the 433MHz range the alarm uses, wireless alarms are designed to tolerate SOME interference on the channels the alarm uses.
By SOME i mean less than 60 seconds of continual interference (as per UL standards for wireless alarm systems).
So any jamming you want to do only has to 1. cover the data packet and 2. last for less than 60 seconds at a time. As you can imagine this isn't too hard if you can switch your jammer on/off easily and have a good idea of where the sensors are.
So to break into a building equipped with a wireless alarm:
1. figure out type of alarm and buy portable jammer for alarm's frequency (cheap)
2. guess where the sensors are
3. key the jammer when you are about to trip a sensor. When you do, quickly tear it off the wall / smash it.
4. steal stuff
5. be out in less than an hour so the alarm doesn't miss any supervision packets. And if it does miss one chances are it'll create a 'trouble' alarm not a 'burglar' alarm; no cops will be called.
Any security system can be beaten- there is no such thing as perfect security. Wireless sensors can be jammed. Magnetic contacts can often be fooled with bigger magnets. Motion sensors can be beaten by holding up bed sheets (as per Mythbusters test).
However if a burglar is crafty enough to jam an RF alarm or fake out magnetic contacts, chances are they are pretty smart and there isn't much you can do to keep them out. Most break ins are dumb criminals doing smash n grab jobs, the alarm is there to blast a 120dB siren in their face and hopefully freak them out enough that they run away.
--IronHelix
This would take forever. The devices to save battery life only transmit a short packet every half hour or so. It varies to prevent repeated collisions with other sensors. 1 missed packet isn't reported as a fault. A series (varies by brand but usualy 3) of missed reports becomes a fault. This fault generation can take hours, plenty of time to raid and be gone again. Use wired for the perimiter.
The truth shall set you free!