I've had servers hacked in the past too, so I know how frustrating it is. It's almost a 'cat and mouse' game between the fix/patch and the hack now though. There's a lot of automated scripts that run around the world hitting every IP they can, and searching for any vulnerabilities. Check your server logs and you'll be amazed at all the hits from the script kiddies! I always make sure IT has the latest updates on the boxes now and it seems to keep them out. It's an ongoing battle though so make sure you have backups, and good luck
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All the best,
E3