i saw this plugin in a Italian server,
the admin make your screen black, but if you have no-flash you can see clearly.
when the admin perceives that you see clearly.
He know you have, no-flash, no-smoke, and maybe wallhack.

I will confess something, I used cheats once, and with a cheat you can you see clearly, without smoke, no flash, and with wh.
on Hide n' Seek, I could see clearly, my screen was not blue like the others.
but now i have a steam account and i dont use cheats xD
i think with the mp_fadetoblack we can make a good plugin anti-no-flash.
sorry about my english, i am Spanish.