A software bug is an error, flaw, failure or fault in a computer program or system that causes it to produce an incorrect or unexpected result, or to behave in unintended ways.1

A computer virus is a type of malicious software program ("malware") that, when executed, replicates by reproducing itself (copying its own source code) or infecting other computer programs by modifying them.2

As Agent Smith was not designed to function how he eventually did, was Smith truly a virus, or is he a bug in the system that Neo exploited with the unintended consequence of uncontrolled replication? I suppose the question can be simplified : is Smith referred to as a virus (or otherwise) either in-universe or out-universe by a canon source?

Note: I say "a bug in the Matrix" because, even though Smith is an independent program, he performs a function in the greater Matrix. He would appear to be highly encapsulated.

  • 1
    Smith copies himself over other programs (or people). Not onto other machines (there is only one Matrix). Thus, he is not a proper virus. Feb 1, 2017 at 17:13
  • 4
    @MarkGardner There's only one internet, too, but it's made up of many machines. I don't think it's stated anywhere that the entire matrix is run from a single hardware platform, or even that that's a sensible way to think of machine technology.
    – Werrf
    Feb 1, 2017 at 17:18
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    @MarkGardner: That's not completely accurate. People would be considered hardware with their own software. The machines force that software to run in a virtualized software environment on their own hardware (The Matrix). People who are unplugged have to hack into the virtual environment in order to access it. We also do not know how programs in the Matrix are actually designed. There may be a hardware component to them, but that detail doesn't really matter to the movie viewer.
    – Ellesedil
    Feb 1, 2017 at 17:59
  • 77
    He's an undocumented design feature.
    – Peter
    Feb 1, 2017 at 18:56
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    He didn't start out as either a bug or a virus. He was an intentional feature, that interaction with Neo altered, freeing him from Machine control, resulting in his viral behaviour. He wasn't a bug; what happened to him was a bug, but [presumably] not one that could have been easily predicted, once Neo had such extensive powers - even given the Machines' collectively extensive analytic resources. Feb 2, 2017 at 6:25

10 Answers 10


Rather than going by technical, real-world definitions, let's use the in-universe description of a virus:

Agent Smith: I'd like to share a revelation that I've had during my time here. It came to me when I tried to classify your species and I realized that you're not actually mammals. Every mammal on this planet instinctively develops a natural equilibrium with the surrounding environment but you humans do not. You move to an area and you multiply and multiply until every natural resource is consumed and the only way you can survive is to spread to another area. There is another organism on this planet that follows the same pattern. Do you know what it is? A virus

By this description/definition, Smith certainly becomes a virus in the later films, reproducing itself and expanding by taking over new areas until it's destroyed everything else.

At the same time, of course, Smith's aberrant behaviour was not intended; it was a fault. Thus it's fair to say that a bug caused Smith to mutate into a virus.


Comments have pointed out that Smith's speech was about biological viruses, and the comparison to humans, rather than a definition of a computer virus. However, the point is that, biological or synthetic, he's displaying the same behaviour that he had earlier condemned. He's become the virus he was describing earlier.

While Smith was undoubtedly talking about biological organisms, the dialogue actually doesn't say that; it just says "organism". The same word is currently used in computer science to refer to simulated life, allowing the same definition to apply to digital life.

Given that he fits the definition of a computer virus given in the question AS WELL as the definition of a virus that he had given in the first film, it makes his fate a case of dramatic irony and character hypocrisy - and definitely, he's a virus.

  • 4
    Agent Smith was describing a biological virus (including humans), not a computer virus, though.
    – Null
    Feb 1, 2017 at 17:27
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    This is a good answer although I agree with @Null in that he is explicitly referring to living organisms and marking them in contrast with machines. It is not him referring to himself as a virus so I think that it doesn't fully answer the question. The reasoning is good though and if we are just using inference then It would work. Feb 1, 2017 at 17:59
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    I agree with both of you that he is explicitly talking about biological organisms in that speech, but that's what makes his later behaviour ironic - when he's freed by Neo, he displays exactly the same behaviour he had earlier condemned. This hypocrisy is part of what makes him an effective villain.
    – Werrf
    Feb 1, 2017 at 18:05
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    That is a ridiculously narrow and literalistic interpretation of that speech. It's absolutely applicable. Computer viruses are named after biological ones! Feb 1, 2017 at 19:19
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    I think it's worth noting the Matrix doesn't really fit into either model. It is a computer system with biological components. To say Smiths viral behavior is closer to a biological virus may not invalidate this. The Matrix had some sort of biological feedback; it doesn't seem crazy that a virus on the system would have biological properties.
    – JMac
    Feb 1, 2017 at 19:22

I would argue that he was a runaway process. Up until his end, he was keeping order in The Matrix, just as he had been told. The problem is that he had somehow transcended his limitations, and was willing to use all of the resources, including those sustaining his fellow residents of The Matrix, to do so.

A "runaway process'' is a process that enters an infinite loop and spawns new processes. This can cause an overflow in the proc table that causes other processes to fail with the No more processes: error message.

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    So, Agent Smith was really while(true) { fork(); }?
    – reirab
    Feb 1, 2017 at 19:08
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    @Withywindle Speaking from personal experience with the mid-2000s OS X kernel, kill -9 isn't necessarily effective against a fork bomb. Even killall struggles, as all of the forking processes may keep forking faster than killall can kill them. Also, the fork bomb may use up all of the available pids before the kill or killall command can be issued, preventing it from starting.
    – reirab
    Feb 1, 2017 at 19:12
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    @Withywindle: To follow up on reirab's comment… what Smith really needed was for The Matrix to define a suitable ulimit for him to cut him off of further resources. Alas as a different commenter observed, Smith's behaviour was to some extent an intended though hidden “feature” included by the architect. Feb 2, 2017 at 1:54
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    @DavidFoerster Smith is definitely pushing the Matrix (v3 I think) towards a buffer overrun. I suppose to the Deus Ex Machina Neo is garbage collection? Feb 2, 2017 at 2:07
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    @reirab: no, while(true) { fork(); } implies self-cloning capability, but Smith was only capable of copying itself over other entities (humans and other programs). It’s like forcing all other existing processes to execute an exec("Smith")
    – Holger
    Feb 2, 2017 at 12:58

In the first episode of the trilogy, Agent Smith is neither bug nor virus. Smith is a security agent that works in tandem with other security agents in the Matrix software-hardware-wetware system, placed there by design, possibly The Architect or by The Source.

Self-interest was infused into Smith by Neo during his attack on Smith just after Neo's virtual resurrection in the first episode. It was Neo's attack on the system security of the Machine World on behalf of humanity. (Neither Smith nor Neo admit to knowing the mechanism through which self-interest was infused.)

After the attack and through to the end of the third episode, the now narcissistic Smith began to impose an increasing threat to The Source (for certain) and possibly also The Architect. Even at this point, Smith remained neither virus nor bug. Smith had become something for which there is not yet an equivalent in the IT world.

The unexpected weapon at the climax of the trilogy was choice. Even self-interest and an emerging sense of purpose did not make Smith autonomous.

The screenwriters' final statement is that the protagonist's autonomy inevitably triumphs over the antagonist's destructive impulse. A potential deeper meaning may be that Clausius's thermodynamic assertion that the change in entropy of any system is never negative has one metaphysical exception: Human autonomy.

This is an intensely humanistic philosophy, which may have lent to the popularity of the trilogy, and it is a philosophy that has not be disproved outside of the fictional world.

  • 1
    I actually really like this answer. If there is no direct comparison in script or from a canon source that explicitly says "Smith is XYZ" we can only say that he behaves similar to previously known system. Since we are dealing with a theoretical constructs that is light years beyond anything we have now, we might not even have the correct terminology to explain it. All we can really say is that Smith provides an impetus for the choice of Neo. Without Smith, Neo need not make a choice in order to save the Matrix. Feb 3, 2017 at 15:55
  • Some of Neo's memory was left behind in Smith, and caused him to behave like a virus. If it was intended he would be a Trojan horse, like Cypher; if not, he was buggy - a security program trusting only its own code. Feb 3, 2017 at 18:38
  • Yes @Withywindle, Smith was the leverage point that required from Neo the ultimate sacrifice. The theoretical concept does already exist, but without real machine intelligence to test it. ... I don't think the screenwriters were commenting on AI as in the case of the Terminator theme. They were commenting on game theory. The Machine World is related more with Pink Floyd's Welcome to the Machine lyrics, a reawakening of the industrial worker's global movement and the May Day thinking of the late nineteenth century. Feb 3, 2017 at 19:42
  • Yes @CeesTimmerman, Smith appeared in some ways to be viral, making copies of himself. Cypher was a traitor, not quote Trojan Horse because he was not a gift from the enemy pretending friendship. ... The real meaning behind the loss of control is not related to AI though. It is about what I wrote in the previous comment. The Machine World already exists and we are already power cells for it. Jaques Ellul's Technological Society already presents, demonstrates, and ultimately proves this sufficiently in its pages. Feb 3, 2017 at 19:47

At the end of the first Matrix, Neo dives into the body of Agent Smith, becomes him, and explodes him. This is the last time that Agent Smith behaved like a normal agent before he began behaving virulently in Matrix Reloaded. You can be certain that at this point in time, Neo overwrote Agent Smith's code. To support this claim, in Matrix Revolutions, during a final confrontation, Agent Smith rants about how something in Neo may have been written onto Agent Smith, and speculates that this may have been a cause for his transformation.

In the first Matrix, Agent Smith functions like an anti-virus program, and Neo functions like a hacker / virus. By Matrix Revolutions, Agent Smith is behaving like the virus. So I would say Neo deliberately reprogrammed Agent Smith to be a virus, and that he is therefore definitely a virus, designed by Neo, and not a bug that happened on its own. By Matrix Revolutions, Neo is rescuing the matrix from the Smith virus, and therefore himself behaving like an anti-virus program. That means Neo underwent a transformation, and Agent Smith underwent a transformation. Character transformations are deliberate and common in well-written cinema, and this turning of the tables becomes more meaningful if they precisely exchanged roles of virus and anti-virus (another reason to conclude virus, not bug).

Lastly, I'd like to point out that Neo's plan to rescue the matrix from Agent Smith and strike a pact of peace with the matrix was a decision he made much earlier. At the beginning of Matrix Reloaded, Neo has an extensive conversation with The Oracle in which she insists that he has already made a decision, but isn't ready to understand his decision yet. Although this can be interpreted to apply to multiple decisions (i.e. his decision to save Trinity. Also note that predictions from oracles in Greek mythology could lend themselves to multiple interpretations and sometimes misinterpretations drive the plot of those myths. Also note that Neo's decision to save Trinity correlated with his belief at the time that the prophecy was a lie), it seems fitting that it likely applies to his decision to reprogram Agent Smith to be a destructive virus. At that point in time, he probably didn't have a full understanding of what benefit it would yield to reprogram Agent Smith; since, in the short-term, it seemed that Agent Smith was simply being a greater nuisance than before. It turns out that there was a not-yet-apparent, logical end-game to reprogramming Agent Smith.

  • I'm not so sure whether the transformation of Smith was intentional by Neo or not. For all we know he may have found it a good attempt of getting rid of Smith.
    – Mast
    Feb 4, 2017 at 11:09

Smith is, for lack of a better term, an intentional bug.

The Matrix has two basic tenets

  1. It must accept the input of the users
  2. Every action has an equal and opposite reaction

In other words, The Matrix is designed to produce the expected outcome of its users. The reason people don't go flying around or bashing walls, is that they literally don't expect them to work that way. Or, to quote the Hindu-ish kid

There is no spoon

The Matrix can't actually enforce gravity. Or stop you from punching through a wall with your bare hand. That's why people like Morpheus can make long jumps and Neo can fly. Literally, if you expect it to happen, it can happen (likely only applies to places where your expectations can shape the outcome, or Neo wouldn't have needed the Keymaster).

The problem for The Matrix is that, the larger the deviation from reality, the larger the breakdown that occurs as it tries to balance things. Part of the deal The One must make to save Zion is that they break down whatever The One is making go haywire and neutralize it, and then reboot The Matrix. Because of the size and scope of The Matrix, there's no way to figure out what the next One will break, or how The Matrix will respond.

The One is, essentially, both the cause and solution of the bug. Zion is, simply put, a way to keep motivating The One to fix the bug and keep The Matrix working.

The catch is, with the second movie, Smith begins to behave like a virus. But a better explanation is that Smith is not a virus per se (where his goal is to keep replicating) but the bug corrupting everything around it. A better term might be something like a buffer overflow, where a bug in a program allows it to exceed its limitations and corrupt other programs around it.

ORACLE: Everything that has a beginning has an end. I see the end coming. I see the darkness spreading. I see death. And you are all that stands in his way.

NEO: Smith.

ORACLE: Very soon he's going to have the power to destroy this world, but I believe he won't stop there; he can't. He won't stop until there's nothing left at all.

NEO: What is he?

ORACLE: He is you. Your opposite, your negative, the result of the equation trying to balance itself out.


I know this is not a direct answer to your question, but there's actually a pretty convincing theory that agent Smith is THE ONE! You should definitely check out The Film Theorist's video on this topic.

Considering Smith calls the Oracle "mum" (it is also said that the Oracle "created the One"), it would make sense to assume that he's a program written by the Oracle, exploiting some bug in the Matrix, which allowed him to disobey the rules ordinary agents have to follow. Bug-exploiting programs are usually called viruses, so I guess he could be called a virus then.

But hey, it's just a theory ;-)

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    Does he really call her "mum" or "mom", or is it "ma'am"? I always assumed the latter, but it's hard to be sure. (Unless someone's got the script.) Feb 2, 2017 at 1:15
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    So this is how deep the rabbit hole goes! Feb 2, 2017 at 7:16
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    @GarethMcCaughan - He calls her "Mom". That's because she's the mother of the current incarnation of the Matrix (per the Architect's speech) however it's highly unlikely that she created the Agents. They're agents of stability and order and she's all about disorder.
    – Valorum
    Feb 2, 2017 at 14:01
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    The script indicates that he calls her "Mom" i.sstatic.net/0B0hw.png. The whole thing is a callback to the earlier speech by the Architect; "If I am the father of the matrix, she would undoubtedly be its mother."
    – Valorum
    Feb 2, 2017 at 14:19
  • 1
    No, mum is the British pronunciation of mom.
    – Eric Lloyd
    Feb 3, 2017 at 19:52

He's neither. He's the balance in the equation that The Matrix is fundamentally built on. The Oracle said this in I think Revolutions.

If you are thinking in computer terms I like to think of it like this. The Matrix has basic rules in the firmware that everything abides by. This includes a balance in an equation. The Architect and the Oracle are another example of this equation balance, one is pure logic and about preserving the Matrix, the other is about "feelings" (can't think of a better word) and breaking it down.

When Neo was created on his "rebirth" in the first film the equation needed to be balanced, I'll go one further than I think was intended and say the Matrix reused the last object that was destroyed to balance the equation… Agent Smith.

What happens beyond this firmware isn't controlled as much, this is where Neo has his powers and Agent Smith can copy himself.

  • I think the concept of object...re-instantiation (if that's the right term)...concerning Smith is an interesting idea. Feb 3, 2017 at 15:57
  • That would explain the Oracle's unhealthy behavior. Feb 3, 2017 at 18:41

I'd label him neither bug nor virus, just part of the programming. I don't think it's true that his behavior at the end was "unexpected". It's heavily implied (if not outright stated) that the Oracle created Smith and likely knew his path. At one point he refers to her as "mom", and she anticipates and expects the things he does in the final acts.

I guess it's a matter of perspective, but it seems like the Oracle wanted everything that happened to happen to break the loop and try new solutions to the problems of man and machine. Like "the One", Smith was a purposefully crafted response to the problems in the "equation".

  • I'm not convinced that the Oracle is a programmer, so to speak. So if she is Smith's creator, how did she do it? Also, "Smith" is a known entity to the Matrix, and doesn't seem like a "new" construct of the 6th cycle or 3rd Matrix. Also, the Oracle is seen as everyone's "mum", not just Smith's, IIRC. I believe that Smith going rogue was an accidental bi-product of Neo's code interference with Smith's.
    – Möoz
    Feb 2, 2017 at 22:17
  • But he isn't part of the programming - he was part of the programming but he has since been corrupted. Smith even says this in his "compelled to stay" speech. Feb 3, 2017 at 15:58
  • Compelled on a "not die" level, not Neo's "love" level. Feb 3, 2017 at 18:47
  • He refers to her as "mom" due to an earlier conversation that if the Architect is the father of the matrix then the Oracle is definitely the mother (or something like that). I don't see any implication that the Oracle made him beyond she was the mother of the matrix, he is something that has been born of the matrix, therefore she is "mom".
    – Rudiger
    Feb 7, 2017 at 5:19

Actually I think he is a pretty aggresive antivirus trying to protect the Matrix from the outer threats, the people. :-D


@Xalorous said that it might be also imagined as an IPS. I think he might have right in a way, and his theory might be closer then mine. E.g.: Smith wants to close the connection with the host (and doing everything in his power to disable the attacker), and by host I mean the human sitting in the chair.

  • Welcome to SFF! Do you have any sources or reasoning for this thought?
    – Rand al'Thor
    Feb 2, 2017 at 13:37
  • My only reason is that that entity hunted Neo who was a threat to the system. Feb 2, 2017 at 13:41
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    The first movie almost blatantly states that he is an agent of the matrix. (Thus his name). I'd liken him to an active IPS (intrusion prevention system).
    – Xalorous
    Feb 2, 2017 at 16:43
  • Not a bad analogy, uses about as may CPU cycles as your typical AV program and is completely useless.
    – Bill K
    Feb 2, 2017 at 19:47
  • If the kernel doesn't protect user files, the IPS must. AV only checks for bad faces, not weird behavior. Feb 3, 2017 at 18:44

I've had McAffee reported as a virus by other antivirus software. This to me looks exactly like agent Smith's dilema (like @Trilarion say in their answer): It's an antivirus program, but it's become a virus in the way it acts. It's not that its purpose is to be a virus, but it certainly is behaving like one. That's why Neo offers to just delete Smith, because it is actually causing more harm than good. So, to me, it is not a virus, but it sure looks like it.

I guess my final assumption would be a flawed antivirus, which would imply some sort of bug happening inside of Smith's code.

  • @withywindle as you say, he was and he's corrupt now. That's preciselly what I'm saying. Be it design flaw or intentional bug, it is a bug. Feb 3, 2017 at 16:01
  • my comment was actually intended for a different question, which is why I moved it. Thanks! Feb 3, 2017 at 16:44
  • Oh, sorry, didn't notice you moved it. Feb 3, 2017 at 16:58
  • In response to your answer: I think flawed antivirus is too specific. I look at it like Smith was rewritten (either accidently or as part of the overall Matrix runtime) and became a process that ran out of control consuming resources until the right type of garbage collection could be run. I actually don't think there is a correct answer to my question, which is unfortunate. Maybe one day the Wachowskis will come out with some more details. Feb 3, 2017 at 17:07
  • @withywindle you're correct about not having enough information. Smith wasn't rewritten from scrath (we would have called it Steve instead) it is still Smith. And it was previously an antivirus. So, now biologically speaking, it looks like an autoinmune disease of some sort. But that's not really applicable to computers anyway. Feb 3, 2017 at 17:16

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