Testing malware should never be taken lightly, even when it's done inside a VM, it's not a toy and it will never be 100% safe to test, especially if you have shared folders on, something you shouldn't do unless you really need to, plus sharing the directories you need is a big mistake. A friend of mine had went through this, he was testing a variant of GPCode and while doing that, he's shared folder was being attacked, some files were caught, but they weren't needed luckily. Most of all, don't test malware if you don't know what your doing!