Harden Network using Sysctl

Harden Network using Sysctl

The core of Linux, Kernel is basically being controlled via Sysctl.

We can Harden Network using Sysctl in a Linux machine.

The /etc/sysctl.conf file contain all the sysctl settings.

The following are a few settings which can be used in /etc/sysctl.conf file in order to harden the network for the server.

[[email protected] ~]# vim /etc/sysctl.conf

Uncomment or add the following lines:

# IP Spoofing protection
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1

# Ignore ICMP broadcast requests
net.ipv4.icmp_echo_ignore_broadcasts = 1

# Disable source packet routing
net.ipv4.conf.all.accept_source_route = 0
net.ipv6.conf.all.accept_source_route = 0 
net.ipv4.conf.default.accept_source_route = 0
net.ipv6.conf.default.accept_source_route = 0

# Ignore send redirects
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0

# Block SYN attacks
net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_max_syn_backlog = 2048
net.ipv4.tcp_synack_retries = 2
net.ipv4.tcp_syn_retries = 5

# Log Martians
net.ipv4.conf.all.log_martians = 1
net.ipv4.icmp_ignore_bogus_error_responses = 1

# Ignore ICMP redirects
net.ipv4.conf.all.accept_redirects = 0
net.ipv6.conf.all.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0 
net.ipv6.conf.default.accept_redirects = 0

# Ignore Directed pings
net.ipv4.icmp_echo_ignore_all = 1

Reload Sysctl in order to reflect the above settings. You need to use the following command:

[[email protected] ~]# sysctl -p

The above should provide you enough protection which will harden network using Sysctl.

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