Last Updated: 2020-01-06 21:05:27 UTC
by Manuel Humberto Santander Pelaez (Version: 1)
Simple Network Management Protocol (SNMP) is a UDP service that runs on port 161/UDP. It is used for network management purposes and should be reachable only from known locations using secure channels.
I reviewed my honeypot today for interesting connections during december 2019. Saw an increase of snmp queries with the following distribution:
This is interesting as attackers are querying for the Community-Based Simple Network Management Protocol version 2 (SNMPv2c) instead of SNMPv2. It introduced GetBulkRequest command to gather large amount of data. SNMPv2c includes SNMPv2 without the SNMPv2 security model, using instead the simple community-based security scheme of SNMPv1.
Our ISC data shows this port was also active during december with a small spike during the first week of 2020:
Shodan report shows many devices connected to the internet with open SNMP port:
And there are domains with an important number of devices with open SNMP port. Source is Shodan:
We can conclude the following:
- There are devices that still have SNMP open to the Internet and the attackers know it. They predominantly search for devices that respond under the SNMPv2c protocol.
- You should not place devices on the Internet with open SNMP services. This is a very cheap way for an attacker to gather intelligence about your network and traffic.
- Please always use secure protocols:
- SNMPv1 send passwords in clear text. SNMPv2 is prone to password hashing attacks.
- SNMPv1 and SNMPv2 are vulnerable to IP spoofing. None of them should be used.
- SNMPv3 is vulnerable to brute force and dictionary attacks. This is the current protocol version. To mitigate the vulnerabilities, you should use IPSec transport connections.
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