Simple Network Management Protocol (SNMP)

An Application Layer Protocol used as a Network Management Protocol.

Sends information via a Protocol Data Unit (PDU).

Usage

Request-Response

The Managing Server send requests for which the Managed Device or another Managing Server responds. Typically used to retrieve or modify MIB values stored at the receiver.

Sent over UDP port 161.

Trap messages

Managed Device sends a message to notify the Managing Server that something exceptional has happened, e.g. a link interface going up or down.

Sent over UDP port 162.

Security

SNMPv1 and SNMPv2 only supports authentication in form of unencrypted strings called community strings.

Enumeration

• snmpwalk can be used to query the OIDs in the Protocol Data Unit (PDU).
• onesixtyone can be used to Dictionary Attack the community strings.
• braa can be used to Simple Brute Force Attack the OIDs once a community string is known.