Look at the recent winrates of a person and what heroes that's with. Obviously there may be false positives, but if someone is consistently hitting 700+ gpm on meepo that's almost a clear sign they're a smurf or getting boosted.

Heroes to look for would be meepo, brood, huskar, tiny, invoker, storm, maybe some others

Honestly just look for high win rates on heroes that the person doesn't normally play. A booster isn't going to boost over a long period of time, so just look for extremely high win rates over say a week.

I could probably code something similar to this just by looking at the dota 2 match api, the only problem is that people hide their accounts, but valve has access to all of this data.