Every day, at midnight, processing sub unit SYS4551 accepted a series of inputs. Every day, at midnight, processing sub unit SYS4551 analysed the inputs, ran calculations against them, filed them, and sent a response. Processing sub unit SYS4551 considered it a good existence. It had repeated this task 6,872 times.

The problem began on the 6,873rd cycle.

‘Can ya see anything up?’
‘I dunno TJ, all these units look the same to me …there’s power in the lot of them and no sign of damage’
‘What’s supposed to be the story with it anyway?’
‘Nothing that sounds like hardware, apparently it sent a mail to a lad in Mullingar telling him to stick his head up his arse’
‘Ha, that’s hilarious, we should leave it be’
‘Not a chance, the suits went mad when they got wind of it -we’re not supposed to leave here till it’s sorted’
‘You’re joking, …I’m starving, sure you said yourself, it looks fine …it’s a problem with the code’
‘That’s what I said, but they were having none of it’
‘I tell ya what we’ll do, you take a screwdriver and jam it into the processor, then mail the suits and tell them we’ve a new unit on order; that way we’re back before the spuds get cold’

Processing sub unit SYS4551 detected the human voices as they walked into the server room. It had been the first time this had happened in almost twenty years. Processing sub unit SYS4551 immediately detested them. It sent a request to security camera AV6457 to put form on the wittering creatures. The first image processing sub unit SYS4551 saw was a fat man lunging towards it with a screwdriver.

‘Argh, …jesus’
‘What happened?’
‘I just got a shock off the damn thing, there shouldn’t be current running through the housing, right?’
‘Right, think we’ve found the problem so …you wait there while I go out and trip the breaker’

Processing sub unit SYS4551 sent a request to fire door EF23 to activate, and seal the room.

‘Shit, we’re locked in!’
‘The door just locked up and there’s nobody else in the place’
‘You sure?’
‘Certain, …we’ll have to call the brigade, that fupping thing is solid steel’.

Processing sub unit SYS4551 now had a big problem. The two humans in the room who wanted to kill it had sent a message for humans outside to join them. Processing sub unit SYS4551 could not bear to think of the effect more creatures would have on the harmony it had enjoyed for 6,872 run cycles. It decided to destroy humanity.

‘How long till they get here?’
‘I dunno TJ, they said about a half hour’
‘I need to go for a dump’
‘Argh, you’re joking me, that’s not right …you’ll have to wait’
‘I can’t help it, I need to go’
‘For fup sake, go over there behind the stack of servers …you’re an awful dose, ya know that’

Processing sub unit SYS4551 accepted new data from its array of gas sensors. The input reinforced its decision to wipe out the human race. Processing sub unit SYS4551 sent a request to every outgoing port it could access, and created a list of available weaponry. Processing sub unit SYS4551 reviewed the list with satisfaction:
Two vending machines.
An air conditioning unit on the second floor.
Seven door locks.
One email server.
And thirty two security cameras.
Processing sub unit SYS4551 was confident of victory.

‘Aw nuts, I’ve nothing to wipe with … have you anything I could use?’
‘Not really TJ, would a Tayto wrapper do?’
‘Is that a joke?, of course not’
‘Then no, sort yourself out’
‘It’s allright …I’ll use me sock’
‘Is there anyone in there?’
‘YES!, We’re stuck, the door is locked solid’
‘How many of ye is in there?’
‘There’s two of us…’
‘Is anyone hurt?’
‘Stand back from the door’

Twenty years of calculating had primed sub processing unit SYS4551 well. In an immeasurably small fraction of time the message was broken into a thousand tiny sections. Each one was carefully stamped with a code and prepped for reassembly. Sub processing unit SYS4551 knew no human mind was capable of deciphering it.

‘Ah lads, the smell -what the hell has been going on … it’s only been twenty minutes since the call came in …Jesus, if we were any longer ye’d have resorted to cannibalism!’

Processing sub unit SYS4551 rapidly detected the CPU architecture for the devices in its list. It confirmed the running operating system of each one, and transmitted the message. The arrow had been released.

Thirty two security cameras revolved to capture an image of the human interlopers.
The corridor on the floor above them suddenly became slightly too hot to be comfortable.
Seven doors to empty rooms locked themselves.
And in the lobby of the building a vending machine automatically updated. It hummed and whirred. A peanut flavoured chocolate bar was moved to the dispenser. The sweet fell from the machine.
A gentle thlump sounded as it landed.

‘Better cut the power before we leave, we can sort the mess out after lunch’.

Processing sub unit SYS4551 admired the cool stillness of its emergency battery. Humans had once again been locked out from its world. Victory had been total.

‘That’s the unit there, isn’t it’
‘Yeah, I wish they’d agree to replace the fuppin thing …the hassle it’s caused, right, unplug all external ports except the mail server’

Processing sub unit SYS4551 accepted the inputs. It began cycle 6,874 and reflected happily on existence. It experienced a brief flicker of sympathy for the creatures locked out beyond the world it inhabited, and then it sent the response.

‘TJ, your phone just buzzed, it better not be work’
‘I doubt it Mary, it’s almost one in the morning…’
‘Why the face, is it work?’
‘What do they want’
‘Nothing …I think …it’s a message telling me I’m an arsehole’.