Technical Tip: How to block specific external (public) IP address via IPv4 policy

[spathak]

Description

This article explains how to block some of the specific public IP addresses to enter the internal network of the FortiGate to protect the internal network. This is specific to configurations that already have inbound firewall policies allowing traffic internally to specific subnets that can be routable externally or that have a VIP as a destination. By default, traffic from external is not allowed internally without a firewall policy configured to allow externally initiated sessions.

Scope

FortiGate.

Solution

Step1: Create an address object

Go to Policy & Objects -> Addresses
Click on 'create new' and 'Address'

Category: Address
Name: Provide any name
Type: Subnet
Subnet / IP Range :   x.x.x.x/32   where x.x.x.x is the  specific public IP it is required to block
                                  x.x.x.x/24   where x.x.x.x is the subnet it is required to block and /24 is the subnet

Interface: Any
Click on 'OK' to apply the changes

Step2: Create IPv4 Policy

Go to Policy & Objects -> IPv4 policy

Click on 'create new '
Name: Provide any name
Incoming interface: WAN interface
Outgoing interface: LAN interface
Source: Select the address object, created above.
Destination: set it to "all"
Schedule: Always
Services: All
Action: Deny
NAT: Enable
Security Profiles:
Enable IPS

Click on 'OK' and place this policy to the top of the IPv4 policy list (by drag and drop) from the ID column.

Note:

In the latest firmware versions (above 7.0) the option for IPv4 policy is replaced with Firewall policy under Policy & Objects.

Note:

If a group of addresses requires to be blocked, select Addresses -> Address Group and select 'Create New'. 

Related article:

Troubleshooting Tip: VIP traffic not matching the firewall policy with an 'all' destination

[jperezgonzalez]

Note: In case a group of addresses require to be blocked, click on addresses select address group and click on create new: