What rough beast?

Synthetic biology seeks to create modular biological parts that can be assembled into useful devices, allowing the modification of biological systems with greater reliability, at lower cost, with greater speed, and by a larger pool of people than has been the case with traditional genetic engineering. We assess the offensive and defensive security implications of synthetic biology based on the insights of leading synthetic biologists into how the technology may develop, the projections of practicing biosecurity authorities on changes in the security context and potential security applications of synthetic biology, and joint appraisals of policy relevant sources of uncertainty. Synthetic biology appears to have minimal security implications in the near term, create modest offensive advantages in the medium term, and strengthen defensive capabilities against natural and engineered biological threats and enable novel potential offensive uses in the long term. To maximize defensive and minimize offensive effects of synthetic biology despite uncertainty, this essay suggests a combination of policy approaches, including community-based efforts, regulation and surveillance, further research, and the deliberate design of security and safety features into the technology.