From Online Manual
type: [ftp=parsed data]parsed content[/ftp]
description: The ftp tag makes ftp hyperlinks. If a single ftp url is placed inside the tags, then a link will be made to that ftp url. How these links are opened depends on your browser, although the default behaviour is to open in a new window.
Links with descriptions can be made using this format. This is an inline tag and no block level tags can be placed inside, however other inline tags can be if nested correctly, with the exception of the email, ftp, iurl and url tags.
Ftp urls will also be auto-linked. If this is not desired, the nobbc tag can be used.
example: [ftp=ftp://somedomain.com]text or more BB Code[/ftp], [ftp]ftp://somedomain.com[/ftp]