See If Someone Has Been In Your Drawers With This Simple Alarm

There’s a spy movie – probably from the [James Bond] franchise – in which our hero is staying in a fancy hotel. It’s crawling with enemies, naturally, and eager to see if one has been snooping in his room while he’s out for martinis, he sticks a hair across the gap in the door. When he comes back and finds the hair missing, he knows the game is afoot.

This hotel safe intrusion detector is what [Q] might have thought up for such a job if he’d had access to PIC microcontrollers and SMD LEDs. [Andy]’s “LightSafer” is a silent alarm for hotel safes, drawers, closets, or even the refrigerator – anywhere where the transition from dark to light indicates an unwanted visit. It’s tiny – only 33 x 21 mm – and is powered by a CR2032 coin cell. A Broadcom APDS-9300 light sensor watches for openings while the PIC monitors a joystick control for the correct PIN entry. There’s no audible alarm; rather, an LED blinks to indicate an unauthorized intrusion and blinks once for every 15 minutes since the event.

LightSafer is simple but effective, with a clever UI that keeps the current draw low and the battery life long. [Andy] used a similar technique for this low-draw cat tracking collar that we featured a while back.

29 thoughts on “See If Someone Has Been In Your Drawers With This Simple Alarm

  1. Now I wish I could remember the author who described rigging a door entry switch to a plain-looking LED digital clock: The switch was in parallel with the “advance time 1 hour” switch. The idea was that you would glance at the clock when you entered your apartment. If the display was two hours fast you would know if someone had entered and then left. If it was only one hour fast, you might expect someone to still be there.

  2. Long story (sorry)….

    I had the dubious experience of an “evil maid” attack when I was traveling to Ca in the same year the company which employed me had been hacked, and Ca had been blamed in the press for the hack. That country was very unhappy that we were holding a conference on their turf, so as a company representatives, my colleagues and I received the full experience of being followed and surveilled 24×7.

    We were in a hotel in the middle of the embassy area of the capital, and I ended up being “upgraded” to a very nice room indeed which was quite cheap. I put my stuff in the hotel safe, and I used a serial numbered sticker I carry for sealing things (freebie from a physical security conference: they’re often used on diplomatic pouches. Physical security conferences often have awesome give-aways!)

    I got back, the sticker was intact. Opened the safe (checked the serial number and broke the seal): it was very obvious they’d completely gone through everything. I am sure of this because when I loaded the safe I threw everything in, but when I opened the safe it was totally neat. They’d actually TIED MY SAFE, without breaking the tamper sticker!

    So how did they get in? I got my cell phone and it looked very much like the back of the safe opened up. So they didn’t need to open the safe door: it had a second way in. Reminder: this hotel was in the middle of the embassy district of Bg, and I was in a room which was outfitted for surveillance because they put diplomats in there. Also, in case it’s not obvious, how I got such a gorgeous room for like US$100 a night.

    Anyway, lots of other weird stuff happened, culminating in my colleagues and I confronting the team of young guys clearly following us, and inviting them to dinner. It really ticked them off. It was fun for 24 hours, but after three days it was oppressive and horrible.

    My point in explaining all this is that this is a great idea, but it needs more than just an optical sensor. The safe actually opened up into a corridor between the rooms (which was quite visible when the maid was in the next room – maybe 60cm wide), and that corridor was kept totally dark because it also had one way mirrors. So this wouldn’t have gone off. I would suggest adding an accelerometer, because they will move stuff around in the safe. I’d also suggest a quiet mode.

    BTW, my company metal-shredded my laptop when I returned from this trip.

    Last anecdote: in this room, whenever I turned the room lights on, dim courtesy lights came on for about 60 seconds. If you ever have this happen in a hotel, and the room has lots of mirrors, they are almost certainly one way mirrors and you may be under observation. The 60 second delay allows the guys behind the mirrors to get black felt screens in place, so when the room goes dark you can’t see them and their cameras.

    Of course, tiny cameras are now more commonly used than one way mirrors. But I’m told by those in the know that you still occasionally see them in hotels, and there are some reasons when they’re still useful in addition to cameras.

    PS. Why did they tidy my safe? Because the purpose of this surveillance was not to spy on me. Their interest in me was zero. It was to make sure I knew they were watching, and we were on their turf if we screwed up. I believe their main concern was us talking to local journalists about our company hack, so they wanted us to feel if we did this, they’d know and we’d regret it.

    1. Why did they – as I understand you – completely destroy a laptop which was, as I suppose, perfectly working? Wouldn’t been enough to wipe the disk and re install the operating system? In that way all malicious software is also wiped, or not?

      1. Taking no chances.
        Long ago, (I think it was on HaD) I read an article how a virus kept re-appearing on a Sony laptop, after the disk was scrubbed, and even swapped out. It turned out the virus was in the firmware for the battery management processor, in the battery.
        It may have only been a proof of concept experiment, but I wouldn’t put it past those sneaky Canadians (that’s what [Not James Bond says:] meant by calling the country Ca, right? (smile) Or was California the implied destination? (smile))
        Who’s to say similar firmware “features” couldn’t be embedded in the processor for the mouse, or other circuit?

    1. That’s the one! But wasn’t the first Bond movie “On Her Majesty’s Secret Service” with George Lazenby as Bond?

      edit: Nope, “Dr. No” was first, in 1962. OHMSS was 1969. I always assumed they started with Lazenby and moved to Connery, but no. They actually replaced Connery twice (OHMSS and “Casino Royale”, with David Niven) and then put him out to pasture through most of the ’70s, only to bring him back for “Never Say Never Again” in 1983. I remember quite a few “I’m getting too old for this crap” jokes from that film.

      IMHO, Connery was the best Bond.

  3. I blame YOU. “Oooh I’ve got a sticker from a convention!” They didn’t teach you at that convention to look up the safe on your phone BEFORE you put your stuff in it?

  4. So several people asked what country Ca was.

    No, it wasn’t Canada.

    I forgot I could include markup, so I actually typed C\a, whose capital was B\g.

    And yes, the reason the laptop was shredded was to avoid persistent implants. The work needed to clean out that midrange Dell was simply deemed not worth doing.

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