Trading is unaffected. You can see quotes at any brokerage that allows trading futures, though you may need a paid subscription for access to non-delayed quote data. Look for the symbol XBTF18.

I wouldn't be surprised if this was a DDoS attack, as all bitcoin exchanges have suffered from them, but I don't know what they think they're accomplishing because unlike bitcoin exchanges the CBOE website is completely separate from the trading systems.