Information
An SNMP community string permits read-only access to all objects.
Rationale:
The default community string 'public' is well known. Using easy to guess, well known community string poses a threat that an attacker can effortlessly gain unauthorized access to the device.
Solution
Disable the default SNMP community string 'public'
hostname(config)#no snmp-server community {public}
Impact:
To reduce the risk of unauthorized access, Organizations should disable default, easy to guess, settings such as the 'public' setting for snmp-server community.
References:
http://www.cisco.com/en/US/docs/ios-xml/ios/snmp/command/nm-snmp-cr-s2.html#GUID-2F3F13E4-EE81-4590-871D-6AE1043473DE