A quick peek at the manual indicates that -U and -P set the userid and password for your password protected site. You just published those items to anyone reading the board. I've made the message private so others may no longer read it.
The gw command you provided is incomplete. Please provide the entirety of all gw and related commands used in your procedure.
The shell is likely eating your backslashes. The expression needs to be quoted so the shell's command line processor does not mangle it. And you should have \x80-\xff not \x00-\xff. Also the cat is not needed. Just give the list to gw.