How to disable the DOTA game on my LAN?

Gentlemen! (and Ladies, of course)

First and foremost I must admit that most likely I came to the wrong place with my question and it is strange to read this post from the person who has close enough (so far) relation to the gaming.

Nevertheless, with pain in the heart I’m knocking in all the doors asking for help to solve my problem which name is DOTA and, maybe. all the online (multiplayer) computer video games.

One guy ( which is my, say, brother ) is abandoned all his life, including learning in the college for playing in DOTA up to 14 hours per day ( sometimes even more )

I tried different technical means to prevent him from over-playing but they give no result by different reasons.

In short, can anybody give a hint how to block DOTA in LAN in such way that my participation in that will be hide? otherwise all the efforts is lost…

Thanks in advance