A set of virtual machines (VMs) with different guest operating systems installed is initially booted and prepared to facilitate rapid creation, or “forking,” of a child VM(s) for malware analysis of a software sample. Because malicious code may be packaged for a specific operating system version, subsets of the VMs may have different versions of the same guest operating system installed. Upon detection of a sample indicated for malware analysis, a child VM(s) running the appropriate guest operating system is created based on a corresponding one(s) of the set of VMs. A process in which the corresponding VM(s) has been booted is forked to create a child process. A child VM which is a copy of the VM booted in the parent process is then created in the child process. The sample is then sandboxed in the child VM for analysis to determine if the sample comprises malware.