If the reports regarding 4chan's operations are true, then bitcointalk.org's security is much better than that. Other than SMF 1.x, which we maintain directly, I believe that all of the software we're using is maintained and kept up-to-date. We also offer
security bounties.
But security can't be guaranteed. The last forum hack was apparently caused by a vulnerability in
helpdesk software used by our Web host, not even any failure on our end. It's very difficult to protect against that sort of thing. And zero-day exploits in our custom code, SMF, or any of the software we rely on are certainly possible, even if we try our best to protect against them.
The best thing you can do to reduce the damage in case of another bitcointalk.org hack is to delete your old PMs. If a PM is in an active user's inbox, then we
can't encrypt it, since otherwise the PM-search feature would be way too slow. (One of the top new features on my to-do list is to allow for exporting PMs into a format that eg. Thunderbird can open. The code is 90% done for this. Then it'll be easier for users to purge PMs from their forum inboxes.) You can also enable limited retention in your settings if you consider your IP logs to be very sensitive, though note that this will make it very difficult for you to ever recover your account, since IP logs are a very important piece of data for the recovery team.
I'm really sad that 4chan is down. Hopefully it comes back soon. Even though I haven't been very active there recently, I consider myself a 4channer more than I consider myself an American: it's one of my cultural bedrocks.
Honestly, I'd probably personally contribute quite a bit of money to some project to revive it, if necessary.
(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.)