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1.153 ALMA-09-019930

Information

AlmaLinux OS 9 must not send Internet Control Message Protocol (ICMP) redirects.

GROUP ID: V-269256
RULE ID: SV-269256r1050138

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.

The ability to send ICMP redirects is only appropriate for systems acting as routers.

Solution

Configure AlmaLinux OS 9 to not allow interfaces to perform ICMP redirects.

Create a numbered *.conf file in /etc/sysctl.d/ with the following content:

net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
net.ipv4.conf.lo.send_redirects = 0
EOF

The system configuration files need to be reloaded for the changes to take effect. To reload the contents of the files, run the following command:

$ sysctl -system

See Also

https://workbench.cisecurity.org/benchmarks/27039

Item Details

Category: CONFIGURATION MANAGEMENT

References: 800-53|CM-6b., CCI|CCI-000366, Rule-ID|SV-269256r1050138_rule, STIG-ID|ALMA-09-019930, Vuln-ID|V-269256

Plugin: Unix

Control ID: 02688da4476974edafc126e61821934bbaffb583755a9b0b941e18844c72a8c9