The truthful answer is both yes and no.
Yes we've closed the back door that was used this time to do this. So it can't again be used to hack us.
But in truth you cannot stop a really good hacker. No one can, not even the government with the best security money can buy is able to completely stop them so for sure a small place like us can't.
But we're thinking seriously about dumping this PHPBB software. It just has too many security weaknesses and it's about the most popular free software available which means it's in use on millions of sites so it's a real target for hackers. We're looking into what options we have to move to another software even if it's a paid version to replace this one. Dunno what we'll end up doing.
But no matter what we do we'll never completely stop hackers. That cannot be done.