3.2.1 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 or a file in /etc/sysctl.d/ ending inconf :

- net.ipv4.conf.all.send_redirects = 0
- net.ipv4.conf.default.send_redirects = 0

Example:

# printf "
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
" >> /etc/sysctl.d/60-netipv4_sysctl.conf

Run the following command to set the active kernel parameters:

# {
sysctl -w net.ipv4.conf.all.send_redirects=0
sysctl -w net.ipv4.conf.default.send_redirects=0
sysctl -w net.ipv4.route.flush=1
}

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

See Also

https://workbench.cisecurity.org/benchmarks/13007

Item Details

Category: CONFIGURATION MANAGEMENT

References: 800-53|CM-6, 800-53|CM-7, CSCv7|9.2

Plugin: Unix

Control ID: 4ea0e236a8f1e4e42fad1d37478acb0553d04ce51cf8ae46c4c172583e475364