161 - SNMP

Simple Network Management Protocol (SNMP) runs over UDP port 161 and is used to monitor and manage network devices like routers and servers. It allows querying for system info (e.g. uptime, CPU, interfaces) and is commonly used in network monitoring tools. If misconfigured—especially with default "public" community strings—it can leak sensitive data or be abused in DDoS attacks.

snmpwalk

Enumerate public strings:

snmpwalk -v2c -c public <target>

Dig deeper with specific OIDs:

# System info
snmpwalk -v2c -c public <target> 1.3.6.1.2.1.1

# NICs
snmpwalk -v2c -c public <target> 1.3.6.1.2.1.2.2

# Users
snmpwalk -v2c -c public <target> 1.3.6.1.4.1

# Running processes
snmpwalk -v2c -c public <target> 1.3.6.1.2.1.25.4.2.1.2

# Open TCP ports
snmpwalk -v2c -c public <target> 1.3.6.1.2.1.6.13.1.3

Or grep for keywords:

snmpwalk -v2c -c public <target> | grep -Ei 'user|admin|name|password|pass'

onesixtyone

nmap

snmp-check