Hardening your TCP/IP stack

For any given operating system, tuning of the TCP/IP stack can be performed by the system administrator. Changing the default values of TCP/IP stack variables provides another layer of protection and helps you to secure your hosts in a better way.

This is all about determining and making decisions about how many connections the server can maintain in a half-open state before TCP/IP triggers SYN flooding attack protection. This simply means that to configure the threshold value of the TCP connection, requests must be exceeded before SYN flood protection is triggered.

The following parameters can be adjusted on an operating system level to tune TCP/IP stacks. These are not only applicable to the operating system, but also to network devices such as firewalls and load balancers, which allow you to fine tune TCP stacks:

• TcpMaxHalfOpen
• TcpMaxHalfOpenRetried
• TcpMaxPortsExhausted
• TcpMaxConnectResponseRetransmissions

We will discuss DoS attacks in detail in the next section.