It was originally published in Isaac Asimov's Science Fiction Magazine, May 1984 and has appeared in several anthologies since. It is available online here.
Charles Kluge, a recluse, appears to have committed suicide & left his property to Victor Apfel, a neighbor (& the narrator) he barely knew. Forensic investigation of the vast computer installations at his home will reveal the lifestyle of a super-programmer & a super-criminal.
Through the investigation, we'll see two more apparent suicides: of Detective Osborne, the cop investigating the case, & Lisa Foo, the woman doing the forensic investigation of Charles' machines & software. And Victor will be left an absolutely frightened & broken man.
You see, while having his hacking fun, Charles had stumbled upon a piece of software running on NSA's computers. We never learn the true nature of this software beast, but get enough indications that it's an AI run amok, that it exists without the knowledge of NSA, & that it is the real murderer of the 3!
Variety SF, John Varley's "Press Enter _" (novella, AI): Lifestyle of a computer hacker & criminal
"It's about a man that is thinking to be controlled by the electrical devices in his home."
"This is a recording. Please do not hang up until—”
I slammed the phone down so hard it fell onto the floor. Then I stood there, dripping wet and shaking with anger. Eventually, the phone started to make that buzzing noise they make when a receiver is off the hook. It’s twenty times as loud as any sound a phone can normally make, and I always wondered why. As though it was such a terrible disaster: "Emergency! Your tele- phone is off the hook!!!”
"Press Enter ▮"
"I remember he starts a relation with a girl with t-shirt, big tits, a dental appliance (tooth brace) and very clever."
Where does one start in describing Lisa Foo? Remember when newspapers used to run editorial cartoons of Hirohito and Tojo, when the Times used the word "Jap” without embarrassment? Little guys with faces wide as footballs, ears like jug handles, thick glasses, two big rabbity buck teeth, and pencil-thin moustaches...
Leaving out only the moustache, she was a dead ringer for a cartoon Tojo. She had the glasses, and the ears, and the teeth. But her teeth had braces, like piano keys wrapped in barbed wire. And she was five-eight or five-nine and couldn’t have weighed more than a hundred and ten. I’d have said a hundred, but added five pounds each for her breasts, so improbably large on her scrawny frame that all I could read of the message on her T-shirt was "POCK LIVE.” It was only when she turned sideways that I saw the esses before and after.
"Press Enter ▮"
"Later in the story she tried to kill herself by putting her head inside a micro-wave oven."
At about ten o’clock that evening Lisa went into Kluge’s kitchen with a screwdriver and some other tools and got to work on the microwave oven.
The manufacturers of those appliances are very careful to in- sure they can’t be turned on with the door open, as they emit lethal radiation. But with simple tools and a good brain it is possible to circumvent the safety interlocks. Lisa had no trouble with them. About ten minutes after she entered the kitchen she put her head in the oven and turned it on.
It is impossible to say how long she held her head in there. It was long enough to turn her eyeballs to the consistency of boiled eggs. At some point she lost voluntary muscle control and fell to the floor, pulling the microwave down with her. It shorted out, and a fire started.
"Press Enter ▮"