Detections
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3.3.2 Ensure packet redirect sending is disabled

Information

ICMP Redirects are used to send routing information to other hosts. As a host itself does not act as a router (in a host only configuration), there is no need to send redirects.

An attacker could use a compromised host to send invalid ICMP redirects to other router devices in an attempt to corrupt routing and have users access a system set up by the attacker as opposed to a valid system.

Solution

Set the following parameters in /etc/sysctl.conf :

 - net.inet.ip.redirect=0
 - net.inet6.ip6.redirect=0

Example:

# printf "
net.inet.ip.redirect=0
net.inet6.ip6.redirect=0
" >> /etc/sysctl.conf

Run the following command to set the active kernel parameters:

# {
 sysctl net.inet.ip.redirect=0
 sysctl net.inet6.ip6.redirect=0
}

Note: If these settings appear in a canonically later file, or later in the same file, these settings will be overwritten

Impact:

IP forwarding is required on systems configured to act as a router. If these parameters are disabled, the system will not be able to perform as a router.

See Also

https://workbench.cisecurity.org/benchmarks/19044

Item Details

Category: CONFIGURATION MANAGEMENT, IDENTIFICATION AND AUTHENTICATION

References: 800-53|CM-1, 800-53|CM-2, 800-53|CM-6, 800-53|CM-7, 800-53|IA-5, CSCv7|9.2

Plugin: Unix

Control ID: b67c6db0333af76fd723928b886cca75a2b0a9dfaab2c9d649bcded3d187c7a2