You don't have to worry about the "hackers" like Grincher, etc. as long as you don't accept their mail or join their lobbies. A lot of the things they were originally able to do -- like corrupting save files -- have been patched by rewrites to the game's code on the 13th. Even if they join a public lobby you're in, you can safely ignore them.
There's been a lot of fear mongering within the community unfortunately, but as long as you don't interact with the exploiters in any way (e.g not accepting mail from people you don't know) you should be more than fine.