Mastering Linux Security and Hardening - Second Edition

Configuring sysctl.conf – Ubuntu

In the /etc/sysctl.conf file on an Ubuntu machine, you'll see lots of comments and a few examples of things that you can tweak. The comments provide good explanations of what the various settings do. So, we'll start with it.

Much of this file contains settings that can help improve networking security. Toward the top of the file, we can see this:

# Uncomment the next two lines to enable Spoof protection (reverse-path filter)# Turn on Source Address Verification in all interfaces to# prevent some spoofing attacks#net.ipv4.conf.default.rp_filter=1#net.ipv4.conf.all.rp_filter=1

A spoofing attack involves a bad actor who sends you network packets with spoofed IP addresses. Spoofing can be used for a few different ...