How to stop spam in my case?

Hey ya, I've read your previous messages about spam & bots, including the post-it with the instructions of how-to make an "human validation" item. But there's a problem... I ingressed in a website with the guestbook installed, and there are files that I can't find in the ftp server. I only have access to:

error_log
gbook.php
index.php
readme.txt
style.php
data/data.txt
data/index.php
data/logauthors.txt
images/index.php
images/(a lot of images)
include/config.inc.php
include/index.php
include/shared.inc.php
language/index.php
language/(a lot of languages)

How to upgrade to human verification? Any patch? Thanks!

Have you tried getting to the files through way of your CPanel instead of FTP?