Software-defined networking (SDN) enables the exible and dynamic configuration of a network, and OpenFlow is one practical SDN implementation. Although it has been widely deployed in actual environments, it can cause fatal aws. In this paper, we consolidate the security threats to OpenFlow mentioned in previous work and introduce a new security checksheet that includes risk assessment methods. We compare the Kreutz et al. threat vectors with the SDNSecurity.org attack list to discover new threats. Our checksheet enables the security of a given OpenFlow network design to be comprehensively assessed. Furthermore, we evaluate the performance of an OpenFlow network with two attack scenarios using the checksheet and identify critical performance degradations.