ModSnmp Manual v3.14 - 3.1. Defining SNMP Users
The Add User page enables you to define the users that are allowed SNMP access.
SNMPv3 uses the User-based Security Model (USM) to authenticate users, and optionally encrypt the data in SNMP messages.
SNMPv1 and SNMPv2c use "community strings" instead of users, and do not support authentication or encryption. If you define a user without authentication, then ModSnmp will allow that user's name to be used as a community string in v1 and v2c messages.
To add an SNMP user, enter the following data and then click Apply:
Note that it is a requirement of the SNMP standard that, for security reasons, passphrases are not stored. If you want to change a passphrase, you should delete and re-add the user.