Can someone explain one thing if i mine via p2poll i have to keep CHNCoin-qt.exe open? or i can close it?
If you are running a P2Pool node yourself, you will have to leave it open. If you are connected to another P2Pool (Such as Bob's), then it's safe it close CHNCoin-qt.
not gpu farm, imo. most likely a cpu botnet. not sure why pool owners allow this, but it is what it is. I'm sure if you check his/her stats throughout the day, you'll see large fluctuations indicative of PCs coming online, or going off.
whats the problem of botnet? If people allow he to use their cpus to cooperate why not?