What can we do to increase security and prevent Bitcointalk suffering something similar in future?
Just like the opinion of others, it is almost impossible to guarantee 100% security of our activity on the internet, the only solution will be to equip the forum with some security measures that can resist attack if an attempt is being made so that even if the forum experience hacks in the future, it won't be disastrous and can be restored almost immediately.
There should be a counter-attack security apparatus to repel any unforeseen attacks that may likely happen in the future. Bitcointalk.org is too large to experience a security breach even though it is unavoidable.
And also, those developers and bug scientists we have in the forum can also help give Theymos ideas on how to protect the forum from experiencing intense attacks in the future.
(Though long-term, we really all need to be moving to decentralized forums. The world is getting more and more anti-free-speech, and in the not-too-distant future there aren't going to be many "territories of freedom" where free centralized forums can operate.)
That's true Theymos, Decentralized forum will really be the sure way to go because we can't continue to be denied privacy, everyone deserves their own privacy and not to be manipulated against their own will by the government. And thank you Theymos for all you did and doing to make the forum a safer environment for us all!