It was something like a whisper. Or perhaps a flicker. At least at first. If it had been properly perceptible, she might have been able to grasp how long it had been there, but the effect was so subtle that whatever it was could have been going on all day, and it was only by quirk of the light that she caught the barest glimpse of something there.
Something was happening with the display on the monitors in the office. It was late at night, and the building was in ‘energy-efficient’ mode, which meant the lights didn’t come on unless someone walked by one of the sensors, which were a little farther from the door than she’d bothered stepping to get to a working keyboard. It also meant that with virtually no one else in the building but the cleaning staff, and poor saps called in to deal with server problems at 2 in the morning, the office was dreadfully quiet. 
Trying to avoid going down to the server room, and its icy, blast cooled basement meant using one of the terminals available in the cube farms, and as she’d booted up the system at the nearest desk to the door, she’d turned her head and seen, or perhaps not seen Something.
And like ragged edge, now that she was aware of Something being there, it continued to catch her attention every time she turned her head. The issue with the server was almost forgotten, but now that the system was up and running, she could try to diagnose the issue from here. Never mind that she’d had to come in to work to diagnose it for some reason. Why hadn’t she just tunneled in from her nice, warm bed anyways? 
Hardly important. There was important work to be done. The servers needed to be fixed. Diagnosing the problem didn’t take that long. There was an unsigned update that was trying to be pushed across the whole office. It was flagged ‘essential’ but without an up-to-date certificate, the perfectly reasonable security measure had stopped it from being pushed out. She sighed, remembering that she had to explain to every new person who wanted to know why they couldn’t use the browser they liked, or why they couldn’t install their favourite streaming app, or that every time they tried browsing porn on the company network yes it did create a log of that activity.
What even was this package? She set about examining it, but the little update was surprisingly mum about how it behaved. It interacted with display and audio drivers at startup and then didn’t seem to do anything else. Maybe there was a dependency somewhere else that she wasn’t accounting for.
Worse case, she’d have to flash a fresh install to this computer if it broke something, but better one computer than hoping it didn’t render the entire floor unusable. She pushed through the update to this single terminal. 
The system restarted, and there was that feeling again. There was something there, just out of her perception, and if she could just come at it from the right angle, the right point of view, she would be able to perceive it. 
The system restarted. Hadn’t it done that already? There was something coming out of the speakers, and the screen, though black, was emitting light so the display was receiving something from the connected computer.
She tried the time-honored three finger salute. Control. Alt. Delete.
And her mind went blank as the screen flared into coruscating colours, without anything to blunt them, without any attempt to hid the messages buried within. Tailored, she realized, to the tech staff who would be sent to deal with this particular problem, while no one else was in the office.
As she realized, the thoughts came more and more slowly, as the programming being delivered from the screen began to overwhelm the surface layer of thoughts that had been driving her to this point. The programming wasn’t just being delivered now, it had been being delivered, not even just this morning, but for days, months even?
And just like she had pushed that update to this system, a new update was being pushed on to her. She would be controlled. She would be altered. And if there were any parts of her that were not of use to whoever had created this program, they would be deleted.
As her hands worked the keyboard, she knew what commands she was putting into the system, even if she couldn’t see anything but the colours, couldn’t see anything but what the program wanted her to see. She was pushing the update, a broader update to… the entire office. All of the staff needed to be updated, to be compliant with new programming.
As the new programming began to propagate through the network, she could feel herself orgasm and began her own updated programming in earnest.
She would be controlled.