While working on video recording of DungCoi worm, there was a random loss of network connection on VirtualBox virtual machine running Windows XP. I was quite pissed off as I couldn't work on new content any further.
VirtualBox keeps updating DNS configuration on guest virtual machines. When a host network adapter changes its DNS configuration, the guest network connection drops. This is pretty much what I've figured out, but it doesn't mean it's an accurate reason.
I have 3 network adapters involved in this. First adapter is for NAT belonging to VMware Workstation, second is for host-only (also belonging to VMWare Workstation) and third one is my Wi-Fi network adapter. For unknown reason, VMware Workstation adapters keep changing DNS configuration. Using both VMware Workstation and VirtualBox could break the connection on VirtualBox guest. However, this keeps occurring even when there are no guest machines running on VMware Workstation. When it comes to my Wi-Fi network adapter, it keeps getting different DNS servers, but they don't change that often.
To fix this issue, check all listed DNS servers in network adapter on VirtualBox guest machine. Find all host adapters that have those DNS server addresses and either apply static DNS server addresses, or temporarily disable.
You can check the video about fixing this problem here.