Ensure TCP SYN Cookies is enabled

OrtaDüzey 1Otomatikcos

Açıklama

When tcp_syncookies is set, the kernel will handle TCP SYN packets normally until the half-open connection queue is full, at which time, the SYN cookie functionality kicks in. SYN cookies work by not using the SYN queue at all. Instead, the kernel simply replies to the SYN with a SYN|ACK, but will include a specially crafted TCP sequence number that encodes the source and destination IP address and port number and the time the packet was sent. A legitimate connection would send the ACK packet of the three way handshake with the specially crafted sequence number. This allows the system to verify that it has received a valid response to a SYN cookie and allow the connection, even though there is no corresponding SYN in the queue. Attackers use SYN flood attacks to perform a denial of service attacked on a system by sending many SYN packets without completing the three way handshake. Thi...

Nasıl denetlenir

Denetim yöntemi: Kabuk komutu

shell

chk() { p=$1; allowed=" $2 "; case $p in net.ipv6.*) [ -d /proc/sys/net/ipv6 ] || return 0;; esac; v=$(sysctl -n "$p" 2>/dev/null) || { echo "$p: not available"; return 1; }; case "$allowed" in *" $v "*) ;; *) echo "$p is $v (running)"; return 1;; esac; sd=$(readlink -e /lib/systemd/systemd-sysctl || readlink -e /usr/lib/systemd/systemd-sysctl); f=$("$sd" --cat-config 2>/dev/null | grep -Po "^\h*${p//./\.}\h*=\h*\K\H+" | tail -n1); [ -n "$f" ] || { echo "$p is not set in any sysctl configuration file"; return 1; }; case "$allowed" in *" $f "*) ;; *) echo "$p is $f in configuration"; return 1;; esac; }; if chk net.ipv4.tcp_syncookies 1; then echo compliant; fi

Beklenen çıktı: compliant

Nasıl düzeltilir

Düzeltme yöntemi: Kılavuz veya altyapı yaması

Set the following parameters in /etc/sysctl.conf or a /etc/sysctl.d/* file: net.ipv4.tcp_syncookies = 1 Run the following commands to set the active kernel parameters: # sysctl -w net.ipv4.tcp_syncookies=1 # sysctl -w net.ipv4.route.flush=1 /etc is stateless on Container-Optimized OS. Therefore, /etc cannot be used to make these changes persistent across reboots. The steps mentioned above needs to be performed after every boot.

Özellikler

İşletim sistemleri: Herhangi biri
Etiketler: container-optimized-oscos
Referans: CIS Google Container-Optimized OS Benchmark v1.2.0 - 3.2.8 Ensure TCP SYN Cookies is enabled

Bu ana makineyi denetle

Bunu denetleme izniniz olan bir makinede çalıştırın. Tarama salt okunurdur.

shell

tmaegis scan --target cos