You have unlimited access to all of the world's information. Source code, books, electronic information, monuments with text on them, tattoos with text, you name it. If it has information encoded has text, you can manipulate it without detection or interference.

You are trying to wreak havoc. The problem is, you can only make one small (1 character) change to only 1 thing.

What will you do to create maximum destruction, measured in terms of:

  1. casualties

  2. monetary loss

  3. societal chaos

Note: If you so choose to modify source code of any kind, you can recompile the code as well (without anyone noticing).

closed as primarily opinion-based by JBH, Mołot, March Ho, Monica Cellio Aug 17 at 1:18

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

  • "you can only make one small (1 character) change to only 1 thing." You can add or remove only 1 character (1 character change) to only 1 thing. – Blondie Aug 16 at 19:49
  • wasn't one of the space shuttle disasters due to a conversion error between metric and imperial (or something like that)? I reckon changing the unit symbol would wreck havoc on many just to choose which one! – EveryBitHelps Aug 16 at 20:51
  • @EveryBitHelps That was one of the mars landers. Now they do all physics in metric, where the calculations are much easier anyways. – pojo-guy Aug 16 at 21:23
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    Please use the edits to improve the question, not to go against our "be nice" policy. – L.Dutch Aug 17 at 3:25
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    @Guran It is unfortunate that your answer won't get more attention, but there needs to be a major shift in the priorities of all the automatically-appointed mods. Who cares if there is some wiggle room in the question..the point is to foster creative thinking and produce interesting answers. Which it did. – Blondie Aug 17 at 14:36

17 Answers 17

Thou shall now kill. (Inscribed in a stone tablet)

In the original Hebrew, change לא ("thou shall not") to לו .לו by itself means "to him" or "for him" or something similar (hard to explain exactly). But together with other words it is sort-of possessive, sort-of permission. It would become something like "For him is to kill".

There are actually places in the Hebrew original (but not in the 10 Commandments) where לא is normally read/understood to mean לו or vice versa, giving the sentence the exact opposite meaning from the way it is written, but with the same pronunciation. See for example Leviticus Chapter 25, Verse 30 where the phrase translated as "then the house that is in the walled city" is actually written in Hebrew לא which would mean "then the house that is in an unwalled city" but is traditionally read in Hebrew as לו and therefore translated (as per traditional Jewish reading of the verse) "walled" instead of "unwalled".

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    All the other answers are good, but this one is terrifying. – Cort Ammon Aug 16 at 20:14
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    @AngelPray Errors can be caught. If a human constructed thing misbehaves, we'll turn it off and it stops misbehaving. But messages from a deity can be as irrational as they want, for how could a human mind comprehend the greater plan of a deity? – Cort Ammon Aug 16 at 20:17
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    @CortAmmon But why would anyone think it's a message from a deity? Surely, if religious people were to walk past a monument of the ten commandments and see that the 6th one was changed, they'd simply assume that some cheeky/evil group had somehow tampered with the monument. I doubt they'd suddenly go on a killing spree. – AngelPray Aug 16 at 20:23
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    Surely someone would think to check the Hebrew original. Or not. – Guran Aug 16 at 20:30
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    There is a famous misprint of the King James Bible -- Thou shalt commit adultery. A.k.a. the Wicked Bible – Gary Walker Aug 16 at 20:36

Add a non-type-able digit into the password of the suitcase known as "the football" which is always in the possession of a secret service agent in proximity of the President. If you don't let anyone know what you've done, you could possibly save almost 7 billion lives.

And since chaos, bedlam and destruction are natural byproducts of human life, you would thereby be responsible for all the harm we do from now through the end of time.

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    this one is oddly happy and I like it – Nic Hartley Aug 16 at 21:19
  • More like 400-600 million (the football's destructive potential used as intended, doubled for aftereffects). Still nice thought. – Therac Aug 16 at 21:31
  • Didn't we find out the password for that was "00000000"? Or was it some other nuclear-weapon security feature they had installed but didn't see a need to implement? – Harper Aug 16 at 22:42
  • I’m sure they test the system. And even if it didn’t, it would only last until the next version. – user71659 Aug 17 at 0:18

If I can only change a single keystroke of a single piece of information, I would have to change the original source for the most widely used form of COBOL to render the programming environment inoperable.

COBOL is still one of the most widely used languages for financial software due to several factors. Preventing the programs from operating would throw a large percentage of the world's financial markets into disarray, doing catastrophic (though, sadly, not world ending) levels of harm.

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    I think, according to one of OP's clarifying comments, that this would be restricted to only rendering one programming environment inoperable. – maxathousand Aug 16 at 21:53
  • @maxathousand Maybe, but the Federal Reserve runs America's financial system's computers. It still takes a day or longer and only on weekdays to process inter-bank transfers in America. And upon America's financial system runs much of the world's financial system. – noɥʇʎԀʎzɐɹƆ Aug 16 at 23:57
  • @maxathousand That's why I noted that I would target the most widely used form of COBOL. Since I have access to the worlds information, it would not be hard to figure out what version to target. – GOATNine Aug 17 at 12:40

In the (very popular) language C; the difference between equals and not-equal is one character; the "!" characterSo

if ( X == Y ) LaunchAllBombs();

could be changed to do something

if ( X != Y ) LaunchAllBombs();

And "LaunchAllBombs()" will be executed precisely when it should not be.

This is true in other languages as well. Likewise, it could exist in banking:

if ( X == Y ) SellAllStocksImmediately();


if ( X != Y ) SellAllStocksImmediately();

Causing a market crash and the loss of fortunes.

I'm not saying there are any such routines, but taking a catastrophic path does exist in both defense code and automated trading code, in satellite code, etc. A terrorist would likely look for exactly that.

  • Yes, and this would obviously still compile so it wouldn't be detected. The existence of routines of this nature is suspect though. – Blondie Aug 16 at 19:59
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    Any code that can take a catastrophic path (and those definitely exist, e.g. to launch missiles or sell stocks) must have decisions that cause it to take that catastrophic path; inverting the sense of that decision will cause it to take the catastrophic path when it should not. I am a programmer that has worked for the dept of defense coding battlefield weapons, and for American intelligence agencies coding sensors and listening devices, and for banks coding credit card transaction approval decisions. These kinds of paths exist; as a matter of necessity; a final decision must be made. – Amadeus Aug 16 at 20:10
  • If bot the actual missiles, you could always trigger a missile detection system during a cold war and try to get them to launch the missiles themselves. – Clay Deitas Aug 16 at 21:05
  • @ClayDeitas Except, they'd be aimed at you, right? Trigger both sides to launch, that would cause maximum destruction; but they would use two different codes; so not in scope of this question. – Amadeus Aug 16 at 21:07
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    Once one country launches its only a matter of time before other countries do. "The only way to win is to not play the game." – Clay Deitas Aug 16 at 21:19

I will change one codon in the DNA sequence that lets mammals produce haemoglobin. Everyone dies quite quickly, as they run out of red blood cells containing functioning haemoglobin.

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    Unfortunately, unless you could make this change simultaneously to every single person's billions of cells, this doesn't work. The parameters are such that you would only be able to change 1 DNA strand on 1 cell on 1 person, hardly a catastrophic result. – Blondie Aug 16 at 20:02
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    @Blondie I'm confused. Why would this work? DNA is not information encoded as text. Quite the contrary, it is us humans that decided to encode the actual sequences of Amino acids that make up strands of DNA into text so as to better study them. So surely, one would only be able to change all the records of this gene and not the gene itself? The gene is not made out of Ts, Cs, As and Gs. Only the representation of the gene is. – AngelPray Aug 16 at 20:09
  • @AngelPray what is the difference between changing polarities in solid state storage and changing a hydrogen bond in a molecule? – Renan Aug 16 at 20:22
  • Yes, but the 'encoded as text' requirement is somewhat loose for the following reason: Modifying a program or file by 1 character is essentially just changing one memory register from one state to another. From the hardware level, the voltage level of the transistors in memory are not encoded as text either, but us humans use text to ultimately encode voltage levels in the transistors. Obviously genes aren't made out of letters, neither are transistors, but hopefully you see the parallel between the two and why it is acceptable to accept this answer. – Blondie Aug 16 at 20:26
  • Frameshift mutations are much more devastating than single letter changes. Shame the question didn't allow for removal or deletion of a letter . . . – FoxElemental Aug 16 at 21:55

Based on the precedent set by Mike Scott's answer as I understand it:

Change the value of G or any other universal constant.

For instance, $G = 6.674×10^{-11} N·kg^{–2}·m^{2}$ becomes $G = 6.674×10^{-91} N·kg^{–2}·m^{2}$ and the entire universe falls apart.

  • From my interpretation this isn't possible in this scenario; though a neat idea. The OP states all of the worlds information which should probably have an apostrophe in it for clarification. Also, wouldn't this just change the way the universe works? Obviously it would destroy a lot all at once, but eventually wouldn't things settle back down? – PerpetualJ Aug 16 at 20:44
  • @PerpetualJ It would cause the universe to become inhospitable to human life (or any life that we know of). Gravity would become so incredibly weak that planets and stars and such would simply fall apart. And when you say that this wouldn't work because OP talks about the world['s] information, do you mean to say only information on Earth can be affected? If that's the case, then I agree that you couldn't destroy the universe using this method. You could still, however, destroy the Earth itself by changing the value of g (lowercase g) which denotes the strength of gravity on earth. – AngelPray Aug 16 at 20:54
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    you cant change a universal constant haha. point me to the location where this information is stored, then you can change it. – Blondie Aug 16 at 21:16

No detection or interference? Ok.

Wait until a major bank is running a permanent, large sum transfer from the Euro to the US dollar, and change the byte storing the exchange rate so that 1 Euro equals 1 quadrillion dollars.

They now have more dollars than had existed a second ago. The dollar is worthless. The US economy collapses. The global economy collapses. World hunger spikes. Panicked refugees spread across the world, overwhelming governments. Total societal breakdown occurs. Terrorists get hold of nuclear weapons in destabilized governments, bomb the world in the name of some religion. The survivors are wiped out by starvation, disease and fallout. Everyone Dies.

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    @Renan, try flipping the highest order bit on the highest byte of an unsigned floating point double. Quadrillions is probably an understatement. – Henry Taylor Aug 16 at 20:55
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    if one modified the proper byte of a floating point value, this is possiblr – Blondie Aug 16 at 21:09
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    This relies on the "no detection" applying to the result of the change, not just the change itself. In any case, I'm guessing the transfer would fail because the system would say something like "error - not enough dollars to make transfer". Also, a bank saying "oh, we just gave them 1 quintillion dollars" does not mean that it actually happens, otherwise why wouldn't someone set up a bank and then make a transfer to give themself a ridiculous amount of money? – Rob Watts Aug 16 at 21:19
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    Computers are just tools in the economic system. The transaction will be promptly reversed - as has happened many times - and will make for a curious piece of news. Worst case scenario (no detection), the bank in question goes down, then gets bailed out if they're major enough. You cannot just claim to have N dollars and use them without other banks agreeing that you do. – Therac Aug 16 at 21:26
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    Foreign exchange doesn't create currency by fiat. In order for a bank to change euros to dollars, someone else (another bank, for example, or another client of the same bank) has to change the same amount of dollars into euros. However, this idea could work if applied to the Federal Reserve, which does create dollars by fiat. – krubo Aug 16 at 21:27

Simply change the defense condition alert status (DEFCON) of the United States armed forces from whatever level it is currently at, likely a 4 or 5, all the way up to DEFCON 1 and wait for someone to blink and start all out thermonuclear destruction.

DEFCON 1 condition means that nuclear war is imminent, it would not itself trigger the launch of any missiles, but it would trigger a lot of armed forces actions that could easily incite further action on the part of the other world powers.

For comparison DEFCON 2 has only been declared twice in history, for the Cuban Missile Crisis and briefly during the start of Desert Storm in the early 1990's.

Two thoughts:

  1. Add apostrophe’s everywhere that is grammatically incorrect.

These change’s aren’t going to cause major monetary loss, but any grammar nerd’s out there may well cause casualtie’s - and certainly some section of society will be in utter chaos. (Sorry - couldn’t resist...)

True, it’s not going to cause major societal upheaval (probably), but if shop signs, printed books, tattoos, religious texts, laws, and so on are all affected, that’s going to be a major annoyance for people.

  1. Change people’s legal gender.

New non-binary gender laws are now being introduced, but most countries still have the M/F option on things like passports, identity cards, birth certificates, and so on. Change all M to F, or vice versa, and make things a lot harder for half of the world’s population to verify their identities (assuming this change can be made in all languages).

Either that, or change all “Mr” titles out there to “Mrs”.

I would change nothing.

Single byte errors happen in computers every millisecond. Single character errors happened in accounting every minute long before computers. Single pictogram errors happened in ancient messages carved in stone.

As a result, no one trusts a single source. Computers check against each other's records. Finances use double accounting, so no single change can do as little as put money into an account. And everyone already expects written, printed or carved sources to contain errors.

Since I can't do anything, I might as well do nothing.

  • This is the only sensible answer here. – JBH Aug 16 at 22:01

Add a digit to a critical economic index.

Dollar exchange value, an oil benchmark, US Federal debt, etc. An immediate 10-fold change wouldn't go unnoticed.

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I would break the C++ language

C++ is widely used for development on specialized hardware. This hardware includes but is not limited to: Airplanes, Factory Automation, Databases, and military equipment.

Breaking C++ would cause most modern passenger aircraft to fall out of the sky. 9/11 used 2 aircrafts, even if nothing hits a major structure the damage would be catastrophic world wide.

Automated Factories would stop production and would cause global shortages in almost every product and could cause equipment failure in chemical plants which could harm people and destroy property.

A number of databases would stop working causing online services to collapse.

Advanced Military hardware would fail in the field, giving most insurgent and resistance movements an easy string of victories.

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    There is no single-character change you can make to 'break' C++, and C++ is compiled to assembly language, so all extant uses of it would be unaffected. Further, if we DO recompile code for any critical device, weapon, aircraft or medical device, we always test the device thoroughly before release. We don't want to kill anybody, or get sued for killing anybody. So we'd catch that is was broken, and investigate, and go back to a previous version of the compiler that worked, identify the culprit keystroke change, blame it on some fat finger idiot and fix it before anything bad ever happened. – Amadeus Aug 16 at 21:27

I would change the configuration files of the traffic light systems. 1 character change would be on the line that controls the green go light and everywhere would be set to Y instead of N.

It wouldn't cause much havoc because the power of 1 character is limited it would most likely just break the 1 system the 1 character is added to.

But if it was 1 line of code....that's explosive.

With 1 line of code I'd put an SQL injection line into the presidents login credentials so next time he logs in it triggers the scripts to launch nukes unbeknownst to him.

1 character has potential to stop things from happening.

1 full line of code has potential to destroy the world.

Hope that helps.

Every number and letter consists out of bites. Bites consist out of a string of one's and zero's. Change every bit that means "1" into "0".

Planes crash as every Electronic becomes useless, cars lose their steering and brake assists, all economies that have ties to digital connections collapse dragging the world into disarray and every research project and all information we havent written down is erased. All food normally grown through electronic assists breaks down and famine sweeps the world as refrigeration and food production collapses. Nuclear powerplants have massive failures as the quadruple redundancies with pumps and whatnot all fail simultaneouslu and meltdowns cover the earth. A new era dawns for the remaining humans as all electronics are distrusted, assuming they survive the food shortages and radiation.

Delete the Left-Pad Node.js project

The one keystroke here would be the [Delete] key.

With left-pad removed from NPM, these applications and widely used bits of open-source infrastructure were unable to obtain the dependency, and thus fell over during development and deployment. Thousands, worldwide.

Essentially, a larger portion of the internet ceased to function for a couple days, and if it was an unrecoverable deletion (Node un-un-published the project, an entirely unprecedented move), then it would cause a huge society upheaval.

Presumably, there are other projects like Left-Pad that could also cause a similar issue, Left-Pad is just unique for being so small (and the reason that the Node.js environment is awful: no one should have ever relied on this package in the first place and instead written their own function for it).

Alternatives ("manipulate 1 byte of text" instead of "one keystroke"):

  • Renaming the package
  • Making the package non-compilable (i.e. introduce an error)
  • Changing the file/folder name of the package

If you're in an editor that allows you to comment out a line with a single keystroke, or perhaps paste a pre-copied line of text with a single keystroke, then you could cause a lot of havoc by simply editing the method which determines if a user is authorized to access a system, as outlined by Tom Scott in this video on "The (Fictional) Day Google Forgot to Check Passwords".

I can't think of a way to condense this down to one keystroke if you're not in such an editor, though really, most programs you'd use for hacking would allow you to paste from a thing already on the clipboard, and most IDEs have a line-comment keystroke.

Vandalize an important object in an unstable area. Even a one character change has a lot of potential to cause offense. Since you cannot be detected, people who revere the object would need to speculated about who committed the vandalism. If those who revere the object conclude a particular group is to blame, certainly societal chaos could follow, and perhaps even casualties.

For instance, vandalizing a gang tag could incite gang violence and vandalizing a monument like the Kaaba could prompt a diplomatic sanctions and incite violence from groups already prone to violence.

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