I'm at this step: 'Configuring Snort, the Heart of the Windows Intrusion Detection System (WinIDS)'.
At this point there are two commands, the point of which seems to be to clear the blacklist and whitelist files that are included with Snort. Here's the first one:
'type NUL > d:\winids\snort\rules\black_list.rules'
This actually creates a *new* file called 'black_list.rules', with no content (size zero).
I think perhaps the intention was to clear the contents of the existing file, which is actually named 'blacklist.rules'.
I don't see 'white_list.rules' or 'whitelist.rules', so the other command just creates an empty 'white_list.rules'.