Chapter III: Expounding main network security techniques including data Encryption, Authentication, Kerberos, Virtual Private Network (VPN), Access Control, Security Protocol and Intrusion Detection Systems and Antivirus technique etc.

• 它们是：防火墙技术、信息安全技术，包括：数据加密、身份鉴别、Kerberos鉴别系统、虚拟专用网(VPN)、访问控制及必要的安全协议、网络入侵检测与网络防病毒等。