The disclosed computer-implemented method for monitoring virtual networks may include (1) identifying a virtual network containing at least one virtualized switching device that routes network traffic from a source port within the virtual network to a destination port, (2) providing, within the virtualized switching device, a set of software-defined network rules containing criteria for identifying packets having at least one predetermined property associated with a security policy, (3) intercepting, at the source port, a packet destined for the destination port, (4) determining that at least one characteristic of the packet satisfies at least one of the rules, and (5) in response to determining that the characteristic of the packet satisfies at least one of the rules, forwarding a copy of the packet to a virtual tap port that analyzes the packet for security threats. Various other methods, systems, and computer-readable media are also disclosed.