I am trying to run a Chinese XP on VirtualBox. Everything works out just fine. Then the Chinese XP starts getting a whole load of updates. Since the virtual machine is really getting the internet connection through the VirtualBox program, do I still need to install all the security programs in the virtual machine or is the security measure in the host machine enough?

The security on the host box will not help the guest in any way. If your connection is NAT'd in some way, that provides basic firewall protection. But if you are browsing to inappropriate sites in the guest, then you need to add good antivirus protection.

I never bother myself, because I do little browsing in my guests, and then only to sites which are not a problem. ... JDH