Hardening SNMP on CentOS/RedHat/Fedora Etc.

These steps should be similar across Red Hat type distros.

Before we proceed, lets stop SNMP

sudo systemctl stop snmpd

Disable SNMP Versions 1 and 2c

First we are going to disable SNMP v1 and v2c

You can manually edit the /etc/snmp/snmpd.conf file and comment out or delete every line starting with com2sec, group, access. Or you can run the following sed commands to change it for you.

sudo sed -i 's/^com2sec/# com2sec/g' /etc/snmp/snmpd.conf
sudo sed -i 's/^group/# group/g' /etc/snmp/snmpd.conf
sudo sed -i 's/^access/# access/g' /etc/snmp/snmpd.conf


Create SNMP Version 3 User

Follow the prompts to create a SNMP v3 user.

sudo net-snmp-create-v3-user -ro -a SHA -x AES

Start SNMP

sudo systemctl start snmpd

You should be good to go.

If you are running a firewall, you will need to allow an exception for SNMP, UDP port 161. You may also need to allow an SELinux exception. Check out the last portion of both these articles.

Allowing SNMP Through Firewall