cyberstrikeus 7.1.1 Disable IP Forwarding (Scored)
Profile Applicability
- Level 1
Description
The net.ipv4.ip_forward flag is used to tell the server whether it can forward packets or not. If the server is not to be used as a router, set the flag to 0.
Rationale
Setting the flag to 0 ensures that a server with multiple interfaces (for example, a hard proxy), will never be able to forward packets, and therefore, never serve as a router.
Audit Procedure
Using Command Line
Perform the following to determine if net.ipv4.ip_forward is enabled on the system.
/sbin/sysctl net.ipv4.ip_forward
Expected Result
net.ipv4.ip_forward = 0
Remediation
Using Command Line
Set the net.ipv4.ip_forward parameter to 0 in /etc/sysctl.conf:
net.ipv4.ip_forward=0
Modify active kernel parameters to match:
/sbin/sysctl -w net.ipv4.ip_forward=0
/sbin/sysctl -w net.ipv4.route.flush=1
Default Value
IP forwarding is disabled by default.
References
- CIS Ubuntu 12.04 LTS Server Benchmark v1.1.0
Profile
Level 1 - Scored