Makoto's users had finally passed two hundred.
In a corner of the Gotanda coworking space, Sigma's island had grown a little wider. There was one more desk, and a potted plant Aya had brought in as her own. The aroma of the coffee Mikoshiba ground every morning had become standard equipment on this island, too.
That morning, Mio was looking over the dashboard.
Makoto's ad space was still small. A few dozen ad placements a day, most of them neighborhood shops or small services. Mio's detection engine sifted them before display and dropped anything suspicious before it went out. Ninety percent automatic, the remaining ten percent looked at by a person. Operations were quiet.
Too quiet, Mio thought.
"Himuro, did you find something again?"
Mikoshiba came over carrying two cups of coffee and a small paper box. He set one cup by Mio's hand and opened the lid of the box. A single eclair from a shop he had apparently gone out of his way to buy from sat neatly inside.
"Get some sugar in before your concentration runs out. It affects software quality."
"My fuel is still below the threshold." Mio drew the cup toward her. "That aside, it's the logs that are strange."
Mikoshiba pulled out the chair next to Mio and sat down. It was a spot that happened to be just out of view from Aya's desk. He seemed to be doing it unconsciously.
"Strange how?"
"The accounts' behavior is too clean."
Mio turned the screen slightly toward Mikoshiba. A list of ad placement accounts. Dates. Amounts. Payment methods. A perfectly ordinary, boring table.
"Too clean, meaning?"
"Anything people do always has variance." Mio traced a cluster in the table with her finger. "If shop owners make accounts to place ads, when they make them, what time they post, and how much they spend will all be scattered. Depending on their mood, how busy they are, what's in their wallet. That's normal. But this cluster of accounts has no variance."
Mikoshiba looked at the table. The twenty-some accounts Mio had pointed out. Now that she mentioned it, every one of them had been created in the same week last month, and the placement amounts were small and fell within a similar range. The types of cards used for payment were similar, too.
Mio pulled out just that cluster and plotted the points along each axis. Time of placement. Amount. Length of the text.
Once before, a similar picture had produced an answer. The people who had mixed fake popularity in with real users. That time, the "clock" had given them away. Bundle the times the flock moved, and the peak that should have skewed toward the middle of the night was smoothed flat, the same height wherever you sliced the twenty-four hours—a flatness that told you at a glance that machines have no night.
But that picture could be drawn because there were tens of thousands of points. With only twenty-some, the shape of a peak doesn't even rise. At this thinness, neither a skew in timing nor variance in amounts could be told apart from "coincidence." The approach of pushing through with distributions couldn't be used yet.
"Small placements, behaving the same as if stamped out," Mio went on. "Looked at one at a time, every one of them is harmless. The amounts are small, and there's no scam phrasing in the text. My engine judges every one of them 'clean' if it looks one at a time. That's why they slip through."
"Slip through and do what?"
"That, I don't know."
Mio said it honestly. There was no reason to lie here.
"All I know right now is that it's 'not like the others.' Who's doing it and for what, I can't say yet. Each one wears an ordinary face, and as a flock a rule rises up. There's a rule in the noise."
Mikoshiba looked at the table for a while.
"What you said before, about 'finding things that deviate from normal'—"
"Anomaly detection." Mio nodded. "A method where you have it learn a huge amount of 'normal' and find what deviates from that. It works even if you don't have a single sample of a scam. Because instead of teaching it 'this is a scam,' you only have to say 'this isn't normal.'"
"So it doesn't need a teacher."
"Right. Without a teacher, it can't explain what's bad. But it can see that something is 'different from everyone else.'"
On the screen, Mio painted those twenty-some in a single color. The moment the scattered points turned the same color, they already looked like a flock.
"What's interesting is that they're 'pretending to be normal.'" Mio's voice dropped slightly. "They smooth the text into something inoffensive, keep the amounts down, and behave so they won't catch on my engine."
Mikoshiba's finger stopped on the rim of his cup.
"They know about the detection?"
"That's possible too. But this is more likely." Mio indicated the cluster on the screen with her finger. "They can do this even without someone on the inside who knows. Throw it over and over, get rejected, and trace the boundary from the feel of it. Whether the ad goes out or not—that's the answer key right there. By getting caught, they're learning the line where they don't get caught. There's no proof. But that's the likelier one."
—Ah, cat and mouse, Mio thought, dryly.
Every time she'd raised the precision of the net at Kotoba, the advertisers' text slipped smoothly away. But the ones tearing the net had always been on the inside. "Don't raise the precision. If ads go down, sales drop." Cleverness at slipping through soon outpaces the corners cut by the ones doing the stopping.
Mio folded that memory into a single line. Only a dry feel was left.
"So, what do we do?" Mikoshiba asked.
"For now, all we can do is let them swim," Mio said, still looking at the screen. "The face, the text—the surface can be changed as much as you like. But the way they're connected remains. One at a time, they're all clean. As a flock, a rule rises up. To call that rule, there still aren't enough points. A social network of two hundred people, the data's too thin. Until more of them come out, I can't see it."
Mikoshiba said nothing, staring at the table.
"Unexpected," Mio murmured. A cold fire lit small, deep in her chest. "How interesting."
Mikoshiba looked up from his coffee.
"Himuro. When you make that face, it's usually trouble."
"Interesting problems are usually troublesome. It's the same thing called by a different name."
Just then, Aya called over from her own desk.
"Hey, Boss. That rumor from earlier, is it true?"
"Rumor?" Mikoshiba's voice slid slightly back into his sales tone.
"The one about Kotoba sniffing around Sigma. The people at your old place are worried about how Makoto's growing, right? Word that the second-generation president's making a fuss, going 'Who the hell are these nobodies,' has even made it to the designer circles."
Mio's hands didn't stop. The word Kotoba stirred no emotion. It was a company she had quit. Not an event that required updating the prior.
Mikoshiba, though, was different.
"It's not worth worrying about." He showed a soft smile. A perfect salesman's smile. "If they're watching us, it's proof we're growing. That's something to be grateful for."
The very perfection of that smile, if anything—Mio thought absently. People hiding something show less variance in their expressions. They become clean, as if stamped out.
Just like that cluster of accounts.
Mio didn't voice the association. There wasn't enough evidence. Besides, reading people's expressions in probabilities wasn't her specialty.
There's a rule in the noise.
Mio could see it, and Mikoshiba seemed not to want her to see it.