For security hardening change the default SNMP v2c communities of public (read only) and private (read write).

Under global configuration mode:

no snmp-server community public

no snmp-server community private

snmp-server community NewRead group readgrp index first secname readview

snmp-server community NewWrite group v1v2grp index second secname initialview

Type show snmp-server community and see the list of indexes in the Community Table (first, second etc…) as there may be others as well created for VRFs.