[support] My Drupal 7.15 just hacked :(

[lamp at afan.net]

Hi,
My development website (Drupal 7.15) setup 2 weeks ago. Only View and
Chaos Tools Suite Modules installed.
I contacted hosting company and they said it's compromised through FTP
-what I don't believe (if it's truth I'm really screwed because there is
tons of other sites too :( )
I got "Security update" message but, since it's development website, I
wasn't rushin'

What's chances it's really FTP or something else? No other problems but
"new" index page. Though, they could "planted" something?

Suggestions?

Thanks for any help,
LAMP