I have just upgraded the Hosting Controller to the latest v.2002 on my Windows server, and I found that someone has hacked my server, and defaced the main page of the Hosting Controller http://##.##.##.##/AdvAdmin

The defaced page says that, This site was hacked by : PVH - Moderator of Viet Hacker . Welcome our site : www.viethacker.net

Does anyone has any clue regarding this hacker/hacking? Apart from defacing, what else the hacker might have done??

And what sould I do to secure my server???