In my setting, soldiers carry with them kill-counters; devices that measure the lifesigns of everything in the vicinity and then count one kill if the lifesigns of a given humanoid suddenly ceases to exist without leaving the detection radius of the kill-counter (in order to award soldiers for prowess and also as a high-tech version of similar behaviour amongst samurai and Imperial Japanese soldiers).

How could someone trick a kill-counter to rack up a high score without killing anyone? For reference, this counter works on 16-bit era computer technology, so it’s fairly rudimentary. Is there an obvious, or not so obvious, way to glitch it into registering a kill when none has happened?

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    $\begingroup$ How exactly does it measure life signs? Without knowing what it's looking for, we can't tell you how to feed it false data $\endgroup$ – Kyyshak Aug 2 '19 at 11:45
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    $\begingroup$ If two soldiers are within range of a person when they die, will it register a kill for both soldiers? $\endgroup$ – F1Krazy Aug 2 '19 at 12:26
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    $\begingroup$ people tasked with killing any lifeform are not soldiers, they are fanatical terrorists or exterminators. Soldiers are tasked with taking or holding an area. Even if that requires disabling an enemy force, it perfectly acceptable (and often preferable) to do it by forcing them to surrender or wounding them. Enemy who knows that surrender is not an option will fight A LOT harder. $\endgroup$ – Bald Bear Aug 2 '19 at 13:53
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    $\begingroup$ Please add relevant info directly to the question itself. Comments are transitive and can get deleted $\endgroup$ – dot_Sp0T Aug 2 '19 at 16:11
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    $\begingroup$ "system can also register other life-counters... the closest to the person who died" First, the counting would be absolutely unreliable with the use of ranged weapons. Second, if we are talking about 100s of soldiers and 100s of targets in the same area, this is a challenging application for modern 64-bit computers, let alone 16-bit ones. $\endgroup$ – Alexander Aug 2 '19 at 16:31

Find yourself an inflatable sex doll and a sheep.

Have the doll leaning on the sheep so that the not-so-clever sensor detects a live 60kg humanoid thing.

Throw a rock at the sheep. He runs away.

Now you have a sheep (computer won't care) and a non living humanoid thing.

That's a kill!

Repeat until the sheep can take no more.

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    $\begingroup$ +1 for making me laugh out loud. $\endgroup$ – MongoTheGeek Aug 2 '19 at 16:25
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    $\begingroup$ ... and then which do you choose to spend the night with? $\endgroup$ – Carl Witthoft Aug 2 '19 at 16:54
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    $\begingroup$ Just curious - what do you plan on doing with the doll later? Just asking...no reason... :-) $\endgroup$ – Bob Jarvis - Reinstate Monica Aug 2 '19 at 22:24
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    $\begingroup$ Upgrade: Put a hundred dolls on stands, lined up in a row. Slowly walk several sheep behind the dolls. When one lines up with a doll, it reads as a target. When it moves past, it's a lifeless target. Scale up as necessary for mass production. $\endgroup$ – bta Aug 2 '19 at 22:31
  • $\begingroup$ @bta This reminds me a bit of Minecraft contraptions. $\endgroup$ – M i ech Aug 6 '19 at 11:40

In computer science, a computer that isn't under your physical control can not be considered secure. I would expect about a month before one of the more technical soldiers gets bored, cracks open their counter, figures out how it works, and wires in a button to increase the kill count by one, bypassing the detection circuit entirely. Then they would earn beer money by doing the same thing to other counters. You're not going to get a wireless connection to a central server using 8-bit technology on a battlefield, which is basically the only way to prevent this.

The hardest part will likely be letting this pass casual inspection. Easiest way to do that is to bribe the person doing the inspection, though there are technical ways to do this. For example, the "button" could be a reed switch mounted on the inside of the case, activated by a magnet. That should be invisible unless the actual case is opened. To disguise any signs of opening, I suggest covering the counter with stickers, paint, or the like, or at least scraping it against a rock. Battlefield gear does not stay pristine, and screwdriver pry marks aren't going to stand out.

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    $\begingroup$ "In computer science, a computer that isn't under your physical control can not be considered secure." - This pretty much says it all, even if these were built to cutting edge specifications, once you go handing them off to hundreds of thousands of soldiers, one of those guys will be smart enough just hack the thing. Before you know it, there will be a app for that. $\endgroup$ – Nosajimiki - Reinstate Monica Aug 2 '19 at 20:57
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    $\begingroup$ Lol was going to say the same thing. If I may add - a simple while-loop around the kill counter could be all that's needed. If you want to be careful, just set it so it increments randomly (using import random and datetime in Python for example). Worst case scenario, they implemented this at the hardware level with an adder - send it too many electric pulses and you might accidentally trigger an bit-error, giving you an NaN number of points! What a win!! $\endgroup$ – cyber101 Aug 3 '19 at 19:43

You say that your device works through eletroception, much like a shark nose.

All you need are oscillators set to pulse at around 0.5 to 3 hertz. That's about what you'd expect from hearts on a battlefield (from 180bpm from the most frightened or raging combatants to ~40 from the dying). Keep switching them on and off, moving them around. When your superiors read your logs, it will seem like a true battle.

Or, if the device is really stupid and you just want to rake in the kills... Go to any chicken farm and find the sexers. A sexer is a person who picks out chicks from a conveyor belt and find out if they are male or female. Then see where the males are thrown into and go there. They are usually ground by machinery. The smaller farms can grind hundreds of chicks per minute, the larger ones can do tens of thousands. Just leave your kill counter close to the machine and watch as it goes crazy.

  • $\begingroup$ I wouldn't say that a chick is humanoid, but for a crude computer, maybe $\endgroup$ – Madlozoz Aug 2 '19 at 12:41
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    $\begingroup$ "good work johnson, you counter registered that you killed a thousand six-feet tall soldiers yesterday...wait feet is the one with two ' right? Anyway, it probably doesn't mattter" $\endgroup$ – Borgh Aug 2 '19 at 12:52
  • $\begingroup$ But it's not registering by heartbeat because the whole point is it only reads for humanoid lives, and there's not much difference between heartbeat bpm for say, a dog to a human. It's registering whole nervous activity, not just specifically heartbeat. $\endgroup$ – Locaq Aug 2 '19 at 15:34
  • $\begingroup$ @Locaq only thing that can register that is EEG's. You won't be able to get a remote reading. $\endgroup$ – Renan Aug 2 '19 at 15:35
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    $\begingroup$ @Locaq I suggest you open a new question, and add the science-fiction tag. Point to this one and explain that you have asked before and got answers from a non-sci-fi point of view, and that you want sci-fi answers now ;) $\endgroup$ – Renan Aug 2 '19 at 15:42

Find something that blocks the detection of the kill counter. Say, if a massive wall of lead blocks it, construct such a wall, put a volunteer behind it, give them a beer or something else they enjoy, meanwhile run up and down on the other site of the wall, the kill counter will continuously switch between seeing and not seeing a life sign (other than yours) ... and profit.

  • $\begingroup$ If I clarify that it uses shark-like electroreception of nervous activity, what's a good way to block that? $\endgroup$ – Locaq Aug 2 '19 at 12:06
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    $\begingroup$ All metals will more or less block that; a Faraday Cage is a good example. $\endgroup$ – Glorfindel Aug 2 '19 at 12:08
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    $\begingroup$ So if you put a sheet of metal in front of the detector, it would block it? $\endgroup$ – Locaq Aug 2 '19 at 12:10
  • $\begingroup$ Isn't it easier to put lead or sheet of metal around the kill-counter itself? Or rather next to it, so it does not register a highly suspicious massacre? $\endgroup$ – Bald Bear Aug 2 '19 at 13:47
  • $\begingroup$ @Locaq It will depend on the thickness, and if the sheet is large enough; electromagnetic waves will reflect off other objects and might be able to pass around it, but with much lower intensity levels. It's not unlike visible light which is blocked by most materials, but if there's a lightbulb in a room around the corner, it'll still give some light around the corner. $\endgroup$ – Glorfindel Aug 2 '19 at 13:48

Plan A: Reverse the polarity!

A microphone is a device that receives vibrations from the air and converts them to electrical signals in its own circuits. But if you reverse the flow1 and push an electrical signal into the device (instead of passively receiving the output), then the microphone becomes a speaker, converting electricity back into vibrations.

Your kill-counter device is a bit like that microphone: it receives electrical signals from the air and converts them to electrical signals in its own circuits, which register as "human" if they match a certain pattern. If you know the pattern, or the pattern is hard-wired into the device, a competent electrician could convert one of your kill-counters into a "lifesign broadcaster", pushing the signal back out into the air.

For an individual solder, the plan might go something like this:

  • Pretend you lost your kill-counter. Request a new one.
  • Give the old kill-counter (and some cash) to a guy who knows a guy. When you get it back, it's been modified into a broadcaster.
  • Go out to the "battlefield".
  • Switch broadcaster on. Switch broadcaster off. Repeat.
  • Collect your medals.

1To be pedantic, this "flow" is not "polarity". But I couldn't pass up on a chance to use that title.

Plan B: Integer underflow attack

You know how in video games, if you get the super-duper high score, it eventually flips back to zero?

—Strong Bad, "4 branches", Strong Bad Email

This is the reverse of that.

  • Make sure your kill-counter is at 0.
  • Leave your kill-counter turned off until you find someone who's pretty close to dead.
  • Turn kill-counter on.
  • Do CPR to bring the almost-dead person back to life. Your kill-counter will register this as -1 kill.
  • Congratulations, you have killed 65,535 people.
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    $\begingroup$ Alternatively conceive a child, although Plan B is a confusing name for this option. $\endgroup$ – TemporalWolf Aug 2 '19 at 21:50

On a simple system like this, you could pop open the cover and find the actual sensor, then make one of the power or data wires loose. Then simply moving around and losing data and/or power will cause the processing controller to misread the situation, deciding there's a kill when one of the "blips" goes "dark".

If it's super simple, as you say, there probably won't be an algorithm to re-detect the life form. In fact, it might be missing purposely, since you wouldn't want your soldiers to be missing out on kills when they are repeatedly killing people coming out the same door, window, or cave entrance.

It could be easily discovered, but it could also be written off by standard "wear and tear" of "someone so active". This all depends on how "hardened" the device is supposed to be. Modern military standards for equipment is pretty high, but these things still fail due to how much of a beating they can take. I'd have to assume that some rogue, splinter group isn't going to have the budget or the manufacturing capability to make a truly rugged device, so there's a good chance of these having a high failure rate.


The way you described the device, it is already incapable of fulfilling its main purpose, so subverting is kind of moot.

You didn't mention how it detects who should get the kill. So if people travel in groups, everyone in the group will get a point whenever a single person makes a kill. You could just attend a lot of executions, and come early so you can have a front row seat, to rack up the points.

You didn't account for causality, so people dying accidentally near you would increase your score. A sniper or poisoner would fail to be awarded their actual kills. In fact, friends of the sniper's victims would end up kill-stealing from the sniper. The laziest approach here is to just hang out in an emergency room. Especially being around people who get resuscitated a few times is great, you get multiple kills from each person. Being a journalist following people on suicide missions is also another "easy" one.

You haven't explained in detail how the device senses lifesigns, but most likely there is at least one material that blocks it (if it relies on electric fields, those are blocked with Faraday cages). You just make a box out of that material and have your friend go in and out of it repeatedly, and each one would be a "kill".

As described, the device also awards a kill every time someone leaves its detection radius. So a racecar driver will score a kill for every spectator at every lap. Flying a plane or helicopter at low altitude (eg. above a busy highway) will have similar effects, as would just standing at an airport where passenger planes take off. Or you could find a big cruises ship and just keep stepping in and out of the detection radius. Even walking through a dense city center should do it. My bad - you did say "without leaving its detection radius".

Of course the obvious solution is to just hack the device and overwrite the memory.

  • $\begingroup$ I think you misunderstood the sentence "count one kill if the lifesigns of a given humanoid suddenly ceases to exist without leaving the detection radius" $\endgroup$ – Ben Voigt Aug 4 '19 at 1:15

I'm going to assume you can't just hide behind a wall to trick the system or it would go off every time you enemy took cover and that they system can magically tell a human from an animal. In my mind this system would measure the fading heart beat as a soldier dies, so just have a friend of the person who wants to cheat the system go Daniel Craig's James Bond and have them slow their heart beat until the kill counter goes off. rinse and repeat


As described, this device isn't smart enough to distinguish friend from foe from neutral, or combat deaths from just death by any other cause. So what you do is just hide out in the trauma room of a hospital, or even the triage area of your own army's medical camp. People are always dying in those places. Might as well rack up a few free "kills" on your counter. In fact, you might get extra freebies, any time someone flat-lines but they're brought back with a defibrillator whatever they use to bring people back when they flat-line (I am not a doctor. TV lied to me.), heck, you might "kill" the same target over and over again if they're right on the brink.

  • $\begingroup$ In real life, you don't defibrillate a flatlining patient. Good plan nonetheless $\endgroup$ – Madlozoz Aug 3 '19 at 8:39

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