What are the risks of testing malware in a virtual machine?

I want to test malware in a virtual machine. What are the risks and how can I prevent them?|||Honestly, there are quite a few risks, but they depend on many things. One, if you somehow come across a piece of malware that knows a bug in a virtual machine and uses it, it can infect your computer(very slim). Two, if you mess with a network utilizing malware like a worm or sality. These malware will use your local connection and infect other machines in the network that you use. Three, if folder sharing is set, the malware can access your main drive with ease. Four, if you have a portable device plugged in, a trojan or worm can spread on it and then from portable device to your main computer. Those are all the risks I can think of at the moment. There is a slim chance to none that you will get a virtual machine bug exploited. Don't play with worms or networking using malware without a shut off connection or at all for that matter. Make sure folder sharing is completely closed. Make sure there are no portable devices, or drives present on the computer. Also make sure you have antivirus on your main computer running at all times. I once tested a rogue on a VM and avast blocked access from downloading it, I'm not sure if that had to do with a direct security risk or it was just scanning all urls.