Mastering Linux Security and Hardening - Second Edition

Configuring sysctl.conf – CentOS

On CentOS, the /etc/sysctl.conf file is empty, except for a few comments. These comments tell you to look elsewhere for the default configuration files and to make changes by creating new configuration files in the /etc/sysctl.d directory.

The default security settings for CentOS are pretty much the same as they are for Ubuntu, except they're configured in different places. For example, on CentOS, the spoof protection (rp_filter) parameters and the link protection parameters are in the /usr/lib/sysctl.d/50-default.conf file.

By piping a sysctl -a command into grep, you'll also see that syncookies are enabled:

[donnie@centos7-tm1 ~]$ sudo sysctl -a | grep 'syncookie'net.ipv4.tcp_syncookies = 1[donnie@centos7-tm1 ...