They have account crackers, so, the owner writes random people who joined, put em' in a cracker program, and cracks the pws.
Owner of the server is a member of Hack Forums. I posted up a warning thread on HF as well. Really sad to see a server do this.
The advertisers found a way around the pwn filter "[Server name] . [Net, com, mcph.co etc]" and "[Server name] , [Net, com, mcph.co etc]". By putting a space "." or ", ". @Noobcrew @CypriotMerks @TannerLittle
Or, just don't join a server that someone advertises. They obviously want you to go there for a reason.