Sounds like GitS:SAC[1] season one. Person is Aoi, created The Laughing Man, an impromptu hacker persona, to expose that micromachine corporations were hiding the fact that expensive micromachine treatments were ineffective against Cyberbrain Sclerosis and that an inexpensive vaccine called Murai existed that was effective. The Laughing Man persona was then used by various corporations to profit in various ways.

Or were you thinking of something else with a similar plot?

[1] https://en.wikipedia.org/wiki/Ghost_in_the_Shell:_Stand_Alon...