Security poses an urgent challenge in today's and tomorrow's communications networks. Commonly used network protocols were not designed with security in mind. Moreover, commodity mobile devices and cloud services are directly connected to billing systems, and increasingly sophisticated malicious code is a costly scourge. Furthermore, in the future, when billions of wireless devices such as the sensors in refrigerators, body implants and roadways connect to the Internet, scalable security and management techniques will be necessary. The group's research in network security spans all the above aspects. In particular, the group's research encompasses the following topics: (1) Information-theoretic secrecy in wireless channels, and network coding security; (2) Media access control authentication in wireless networks, and jamming in wireless sensor networks; (3) Secure wireless vehicular communications, and economics of regulating outbound attack traffic from ISPs; (4) Information leakage in smartphones, fault-tolerant secret sharing protocols in sensor networks, and (5) Vulnerabilities and attacks on network architecture and systems.