> Abusing Application Layer Gateways (NAT Slipstreaming)

You might have heard about “NAT Slipstreaming” by Samy Kamkar. It’s an amazing technique that allows punching a hole in your routers firewall by just visiting a website. The attack depends on the router having the Application Layer Gateway enabled. This gateway can be used by anyone inside your network to open a firewall port (totally by design). Protocols such as SIP (Session Initiation Protocol) use it. What I will focus on in this post is the Application Layer Gateway (ALG) and SIP.