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Syncookie (#372)

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* Enabled SYN cookie sysctl.

Signed-off-by: Farid Joubbi <farid@joubbi.se>

* Removed SYN cookies from here since it's a default now.

Signed-off-by: Farid Joubbi <farid@joubbi.se>
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Farid Joubbi 2021-01-15 09:56:29 +01:00 committed by GitHub
parent 16a41412bb
commit d01abb44c0
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2 changed files with 8 additions and 2 deletions
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8
roles/os_hardening/defaults/main.yml
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@ -171,6 +171,14 @@ sysctl_config:
# RFC 1337 fix F1 | sysctl-10
net.ipv4.tcp_rfc1337: 1
# Attackers use SYN flood attacks to perform a denial of service attack on a system
# by sending many SYN packets without completing the three way handshake.
# This will quickly use up slots in the kernel's half-open connection queue and
# prevent legitimate connections from succeeding.
# SYN cookies allow the system to keep accepting valid connections, even if
# under a denial of service attack. CIS Distro Independent 3.2.8.
net.ipv4.tcp_syncookies: 1
# Send(router) or accept(host) RFC1620 shared media redirects | sysctl-12
net.ipv4.conf.all.shared_media: 1
net.ipv4.conf.default.shared_media: 1

2
roles/os_hardening/vars/Amazon.yml
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@ -40,7 +40,5 @@ os_always_ignore_users: ['root', 'sync', 'shutdown', 'halt', 'ec2-user']
sysctl_rhel_config:
# ExecShield protection against buffer overflows
kernel.exec-shield: 1
# Syncookies is used to prevent SYN-flooding attacks.
net.ipv4.tcp_syncookies: 1
hidepid_option: '2' # allowed values: 0, 1, 2