Windows viruses hitting linux via network shares

[Joel Hammer]

Yet another virus is on us. This one comes via windows and when executed
will erase your hard drive, or whatever.
I have a home network with windows clients on it. So far, nobody has done
the unthinkable, but they might some day.
I have all the boxes hooked together with a samba network. Seems to work OK.
I have all the clients as guest = ftp. This means that they couldn't write
to most of my directories (or erase them) but there are plenty of files and
probably some directories which are world writeable and erasable.
So, question is, if one of these malicious viruses executed on a windows
client, how much damage would one expect to the world writable directories
and files on my linux boxes (Forget the windows boxes. I would gladly tell
my windows users it was a shame.)
While I await the answer, I am going to change all my shares to read only.
On second thought, using the magic of samba, I'll let the linux boxes have write privileges.
Joel