Today, network traffic often uses more than a single protocol: it embeds another protocol into a transport protocol. For example, HTTPS is HTTP protocol embedded into the Secure Socket Layer (SSL) protocol. SSL encrypts HTTP traffic and many firewalls simply permit encrypted traffic pass without thorough inspection. This is not an optimal solution from a security aspect, and PNS has a better solution to this problem: it decrypts and inspects the SSL traffic, and passes the data stream to an HTTP proxy to inspect it. This modular architecture (that is, proxies can be stacked into each other, or even chained together for sequential protocol analysis) allows for sophisticated inspection of complex traffic, for example, to perform virus filtering in HTTPS, or spam filtering in POP3S traffic.