Linux Network stack hardening configuration / sysctl.conf

sysctl.conf

# 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