You won't know until you try—she started to say, and Mio was already moving her hands.
The net she had drawn over the police's carcasses last night. Its shape still lingered at her fingertips. Once you learned how to haul in the root, from then on you could trace it from just one side. She had let that slip herself last night, and Mio couldn't leave it alone.
The company's own logs, always left open. Makoto's raw feed. A tired old waterfall of numbers, bouncing them as fast as they sprang up, and then more springing up. Until now, she had been slugging it out with this waterfall one item at a time. While she erased one, three more sprang up. Taking them out one by one was a losing line. The same as the Hydra—Mio knew that by now.
"This net isn't a tool just for the police's pile," Mio murmured. "It should work as is on the ones springing up here every night, too."
"Hold on," Mikoshiba said from behind her.
"You built that net on the police's data, which has the flow of money in it. Our feed doesn't have a money layer. No frozen accounts, no bands of IPs. What we have is click rates, time on page, and report history. The types won't mesh, will they?"
It was a fair question. Mio answered without taking her eyes off the screen.
"The contents of the dots are certainly different. Theirs are dead accounts; ours are reactions to live ads. Put side by side, the formats are too different to reuse normally."
"But—"
"What my net looks at isn't the contents of the dots. It's the 'way they're connected.'"
Mio went on talking as she rearranged the graph settings.
"I'm using a net called a heterogeneous graph. It's fine if the node types differ. Bank accounts, user accounts, ads—they can all be placed on the same diagram. As long as the skeleton of how they're connected is the same, the machine sees through it: 'this is the same enemy.' So the net I built over there can be reused here as is."
"In short, the data is different, but the algorithm is the same."
"Right. I just fit it to our data's format and use it."
We have every specimen, Mio thought. The company's own carcasses, discarded in silence every night. The mountain of records the detection had spat out and piled up for months. If you want to know what's happening out in the world, first dig at your own feet, with the same net.
She turned the net toward Makoto's feed.
But the waterfall didn't come into focus.
The dots stayed scattered; the lines didn't extend. Or else lines thickened in strange places. The net, tuned on the police's data, had distributed its weights on the assumption of a money layer. Makoto had none of that at all. The net tried on its own to fill the gaping hole in its features with something else, and set an unrelated popular account right in the center.
"...That's wrong," Mio said, plucking out the cluster and removing it. "The money column is empty, so it's using 'gets clicked a lot' as the crux instead. That's just someone popular. Not a scam."
Fill the hole again. To make up for the lack of money flow, thicken the features that only existed on this side. The same ad text reused. Landings that redirected externally. Accounts that had only just been created, bursting into motion. Which parts of the skeleton to weigh heavily. Mio redistributed the weights several times, sweeping the waterfall each time and discarding the clusters that missed.
Eventually, here and there in the waterfall, a familiar mesh came faintly into view.
Without being shown the money layer, from the connections between accounts alone, the rings had gathered and come into focus.
"—There," Mio murmured. "Even with just the accounts, I could pull them."
Mio tapped a key lightly.
The waterfall, which until then had dropped them one at a time, plip, plip, changed. Dozens of branches extending from a single cluster formed a single outline on the screen. When Mio smoothly circled that whole outline with her finger, dozens of scam accounts vanished from the waterfall at once.
Mikoshiba caught his breath.
Until now, while they took down one, three more sprang up. Now, for the first time, the speed of taking them down had caught up to the speed of their springing up.
Mikoshiba couldn't see exactly what Mio was doing. But he could tell that the water in the bucket—which they had always been scooping out only to have it overflow—was receding in bundles, without a sound, each time Mio's fingers moved. She had stopped counting by hand. Stopped counting, and decided to bundle them instead. Something that simple, and until now no one had been able to do it.
"I stopped counting the branches and grabbed the body. That's all," Mio answered flatly. "But this isn't the end. Tomorrow the root will move again. It's not an opponent you deal with in a single sweep."
Mio glanced at the edge of the screen. The flow of money and data going out from Makoto to the outside. The net drew that far cleanly.
"This is as far as it goes," Mio said, low.
"As far as it goes?"
"What I can draw is as far as 'where' the money and data flowed. Who deliberately sent it there—that can't be seen from the outside."
Mikoshiba looked at her profile.
"Even with the same flow, whether it was stolen and leaked or someone knowingly sent it out, the outward form doesn't change. The intent inside isn't written in the way things connect," Mio continued flatly. "If I tried to fill that in, I'd have no choice but to treat lines that aren't connected as 'connected.' I won't do that."
It would not become a tool for lies. She would not bend the technology in a direction it shouldn't go. That alone was the line Mio had drawn for herself. The net showed only what could be seen. It did not pretend to have seen what couldn't be.
"That's enough," Mikoshiba said. "That line is what makes your analysis trustworthy."
Mio didn't answer. She just checked, once, that at the edge of the map, the outer area where the lines hadn't extended was still left blank and white. Fill it in, and it would make a picture. She wouldn't. That was all there was to it.
—A few hours later. Two maps lay side by side on the desk.
A list, by network, smoked out from the company's own feed. And a map of the root, exposing the crux accounts the money passed through. The skeletons of the side being shot at and the side doing the shooting. One from the living Makoto, one from dead carcasses. Dug from separate entrances, they had arrived at the body of the same creature.
The strength drained from Mio's shoulders. She collapsed against the back of her chair.
"This isn't mine to catch."
Mio slid the two maps toward Mikoshiba.
"This is as far as I can go. All that's left is to deliver it to the police."
Mikoshiba's eyes slid over the maps. The scattered damage, for the first time, lay there as a single structure. The detectives who had said they didn't know what to ask. The answer to that question had now become two sheets of paper.
"With this, the police can finally decide 'what to investigate,'" Mikoshiba said, picking up his phone. "I'll give the prefectural police a heads-up. Tell them we can see the structure."
Mio murmured, in a voice half asleep.
"The map is done. The net has started running in-house, too. All that's left is to deliver this—to the people who need it."