There are "hackers"and there are also posters of stupid messages (spammers). Both are a real pain for guestbook owners. On a couple of guestbooks which I look after I now have to approve all postings before they go "public" which means an unfortunate delay. The "spammers" apparently use special software which finds the guestbook and even adds a message automatically. It sounds as though Dimitri's guestbook was "spammed" well and truly.
The worst problem I get is hackers who get in and DELETE ALL the messages. I have to take care to keep a back-up and my notes on how to re-instate it.
Hackers search the net for guestbooks. The web logs show that they go straight to them without coming from any links so must have the direct address. Often I have traced the source to computers in China, Korea, Japan and the USA. What would they be doing looking at a Corfu guestbook?
What do they get out of it ? ... presumably some sort of twisted elation in wrecking something.
Dennis