The moment of the hacker's attack was reported by user Revelator9 on Reddit. He said he contacted Valve, but in the meantime can no longer stream until this issue gets fixed.
Since his stream yesterday, and for the few games he tried today before he had to just stop streaming. A couple of minutes into each game, the entire enemy team all disconnects at once.
Previously, Dota fans discovered an unusual bug with the abilities of Rubick and Spirit Breaker. The interaction of the spells of these two heroes can lead to a game crash and problems with the server.