Care to elaborate more about what you meant by "attack". Thoughts I have addressed this but the worst they could do will be to either bann BTC or put on a high tax for the BTC/FIAT exchanger to discourage people.
Banning BTC will never be a succesful way for them to "attack" BTC because eventually it will just lead BTC deeper underground. Most people will still use it eventhough it has been bann i.e russia
So I think if bitcoin grow up in future, the government will prefer try to put on a high tax for bitcoin than ban it, since if they do ban then they won't gain anything, and if they legalize it than put on a tax, they get profit. If bitcoin really will be banned, I think no one will make a online shop with the bitcoin as the currency, or make other bitcoin website in the country, so the bitcoin will be so hard to developed. If the government may cooperate with bitcoin, they will help to introduce what bitcoin is to society and put high tax on it, but if they may not, they will do anything to make bitcoin is bad thing to society with mass media helping. I guess that's why there were so many news told us several crime cases that related to bitcoin.