The SNMP community string is a shared “secret” among the SNMP management station and the SNMP network agents being managed. This is called a community key because it can be used to define a data-exchanging group of agent and management stations within a larger network. The default key for the PIX Firewall, like many network devices, is public. This is also a routine default entry in most sniffer, mapping, or other reconnaissance tools, so common sense says to change it.