I once heard from another person that someone was making everyone lose connection in the Gym a few weeks ago, then it took them directly to Hall of Frames, which in fact is unusual, I want to find out more about this situation in Worlds."

The only information we have on the issue is available here.

It's important to note the World has not been "hacked", but data packets are being intercepted using Winsock Packet Editor to kick users out of the World (this issue is especially troublesome in the gym).

The person who started this issue calls himself "dbTier1", and claims to be able to "shut down any world and any room" and "modify the Flash files to our preference" (the latter being false).

It's safe to assume that multiple people are doing it based on how often it happens. Why they're doing this is currently unknown, but in the meantime, you might just have to use other Worlds (which don't seem to be targeted).