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The Ubuntu operating system must not allow interfaces to perform Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirects by default.


Overview

Finding ID Version Rule ID IA Controls Severity
V-215151 UBTU-16-030580 SV-215151r610931_rule Medium
Description
Internet Control Message Protocol (ICMP) redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table, possibly revealing portions of the network topology.
STIG Date
Canonical Ubuntu 16.04 LTS Security Technical Implementation Guide 2020-12-09

Details

Check Text ( C-16350r285321_chk )
Verify the Ubuntu operating system does not allow interfaces to perform Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirects by default.

Check the value of the "default send_redirects" variables with the following command:

# sudo sysctl net.ipv4.conf.default.send_redirects

net.ipv4.conf.default.send_redirects=0

If the returned line does not have a value of "0", or a line is not returned, this is a finding.
Fix Text (F-16348r285322_fix)
Configure the Ubuntu operating system to not allow interfaces to perform Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirects by default with the following command:

# sudo sysctl -w net.ipv4.conf.default.send_redirects=0

If "0" is not the system's default value then add or update the following line in "/etc/sysctl.conf" or in the appropriate file under "/etc/sysctl.d":

net.ipv4.conf.default.send_redirects=0