Information
The tcp_tcpsecure parameter value determines if the system is protected from three specific TCP vulnerabilities: The values are ORed together. If all three values are to be set the value to set is: 1|2|4 (or 7).
Fake SYN - This is used to terminate an established connection. A tcp_tcpsecure bit-value of 1 protects the system from this vulnerability.
Fake RST - As above, this is used to terminate an established connection. A tcp_tcpsecure bit-value of 2 protects the system from this vulnerability.
Fake data - A hacker may inject fake data into an established connection. A tcp_tcpsecure bit-value of 4 protects the system from this vulnerability.
Rationale:
The tcp_tcpsecure parameter should be set to 7. This means that the system will be protected from TCP connection reset and data integrity attacks.
Solution
In /etc/tunables/nextboot, add the tcp_tcpsecure entry:
no -p -o tcp_tcpsecure=7
This makes the change permanent by adding the entry into /etc/tunables/nextboot.
Default Value:
tcp_tcpsecure = 0