Most enterprises store information on electronic media. A small USB drive may contain core confiential technical information or years of research results. As the value of information assets increases, illegal information trade has become industrialized. Hackers can steal and employees can leak information. In the mobile Internet era, information leaks are easier with mobile apps and social networks. As the information transmission media, networks are the key in data leak prevention. To prevent network-layer data leaks, the NGFW must be capable of keyword fitering and anti-evasion. Common evasion behaviors include: