I know about a couple of fora that has been 'carpetbombed' by chinese, russian and eastern european 'visitors', most IP's adressed at Moscow, StPetesburg and Kiew.
Probably robots, and a lot is spreading gayporn.
To close the ports for IP blocks logged is one of the actions to keep it out.
Such 'attacs' also steal a lot of bandwidth as well as fill the threads with garabage that again make lot of work for mods and admin.