As shown at the end of the episode. Nanao put out the virus. However, what was unexpected was his death. So could the one behind it be the Metropolitan Police? Stoll Nanao smiling as he died makes you wonder who pulled one up over him? Though the various people going after the Superintendent-General is scary because how anyone could be influenced. The interesting thing here all of these people are innocent because the it is 100% the virus fault, which shows how dangerous a virus could be.
The chief makes an interesting note that this all started as a seed from 6 years ago. The various “Laughman Man” started as a seed. Copies without an original. But you think a virus as something that has a starting point and effects others? If the copies are standalone complex what is their goal? Could it be possible these Laughing Man learned from the Death Thread which grew the copies. Though what truly caused it is intriguing.
Also interesting that there are things that the Superintendent-General is hiding. Will be interesting if this is the true root cause of the incident.