The ipPermitDeniedTrap notification comes from the CISCO-STACK-MIB, and indicates that a host is trying to access this switch, but is being denied due to an ip permit list. The notification includes two varbinds, ipPermitDeniedAddress and ipPermitDeniedAccess which should tell you who is trying to access this switch, and what protocol that host is using. Typically, the protocol is SNMP, but it could also be telnet or SSH.