| name | CIS Ubuntu 14.04 LTS - 3.1.1 Ensure IP forwarding is disabled |
| description | Verify that IP forwarding is disabled to prevent the system from acting as a router |
| category | cis-os-hardening |
| version | 2.1.0 |
| author | cyberstrike-official |
| tags | ["cis","ubuntu","ubuntu-14.04","level-1","scored","network"] |
| cis_id | 3.1.1 |
| cis_benchmark | CIS Ubuntu Linux 14.04 LTS Benchmark v2.1.0 |
| tech_stack | ["ubuntu","linux"] |
| cwe_ids | [] |
| chains_with | [] |
| prerequisites | [] |
| severity_boost | medium |
3.1.1 Ensure IP forwarding is disabled (Scored)
Profile Applicability
- Level 1 - Server
- Level 1 - Workstation
Description
The net.ipv4.ip_forward flag is used to tell the system whether it can forward packets or not.
Rationale
Setting the flag to 0 ensures that a system with multiple interfaces (for example, a hard proxy), will never be able to forward packets, and therefore, never serve as a router.
Audit Procedure
Run the following command and verify output matches:
sysctl net.ipv4.ip_forward
grep "net\.ipv4\.ip_forward" /etc/sysctl.conf /etc/sysctl.d/*
Expected Result
net.ipv4.ip_forward = 0
Remediation
Set the following parameter in /etc/sysctl.conf or a /etc/sysctl.d/* file:
net.ipv4.ip_forward = 0
Run the following commands to set the active kernel parameters:
sysctl -w net.ipv4.ip_forward=0
sysctl -w net.ipv4.route.flush=1
Default Value
Not specified.
References
- CIS Controls: 3 - Secure Configurations for Hardware and Software on Mobile Devices, Laptops, Workstations, and Servers
- CIS Controls: 11 - Secure Configurations for Network Devices such as Firewalls, Routers and switches
Profile
- Level 1 - Server
- Level 1 - Workstation
