SNMP | 161

Simple Network Management Protocol is a protocol used to monitor and manage devices on IP networks (routers, switches, servers, printers, etc.)

SNMPv1 and SNMPv2c are insecure due to plaintext community strings, so use strong, non-default strings and restrict access to trusted IPs, especially in production, while SNMPv3 offers secure authentication and encryption but is more complex to configure; always limit sensitive data exposure through configs (e.g., /etc/snmp/snmpd.conf on Linux) and firewall rules (UDP 161/162), noting that Windows requires manual SNMP service installation, and Linux logs are in /var/log/snmpd.log

01. Set Up SNMP Service

• Windows

## ------------------| Install
Add-WindowsCapability -Online -Name "SNMP.Client~~~~0.0.1.0"     ## Windows 10/11 (Run as Administrator)
Install-WindowsFeature -Name SNMP-Service -IncludeAllSubFeature -Verbose    ## Windows Server 2016/2019/2022 (Run as Administrator)

## ------------------| Configure SNMP Service
### Configure via Registry
reg add "HKLM\SYSTEM\CurrentControlSet\Services\SNMP\Parameters\ValidCommunities" /v public /t REG_DWORD /d 4
### Configure via GUI
##### 1. Open Services (services.msc), find "SNMP Service", and set to Automatic
##### 2. Right-click SNMP Service > Properties > Security Tab
#####     - Add Community String (e.g., "public", Read-Only)
#####     - Set "Accept SNMP packets from these hosts" (e.g., SNMP Manager IP)
### Allow SNMP through Firewall
netsh advfirewall firewall add rule name="Allow SNMP" dir=in action=allow protocol=UDP localport=161
Restart-Service -Name SNMP        ### Restart SNMP Service
Get-Service -Name SNMP            ### Verify SNMP Service

• Linux

## ------------------| Install
sudo apt install -y snmpd snmp                  ### Ubuntu/Debian
sudo dnf install net-snmp net-snmp-utils -y     ### CentOS/RHEL

## ------------------| Configure SNMP Service
## sudo vi /etc/snmp/snmpd.conf
rocommunity public   # Allow SNMPv2c read-only access
agentAddress udp:161 # Listen on all interfaces (or specify IP like udp:127.0.0.1:161)
sysLocation ServerRoom # Optional system info
sysContact [email protected] # Optional system info

## ------------------| Configure SNMP to Listen on All Interfaces
sudo sed -i 's/snmpd.options=".*"/snmpd.options="-Lsd -Lf \/dev\/null -u snmp -g snmp -I -smux,mteTrigger,mteTriggerConf -p \/var\/run\/snmpd.pid"/' /etc/default/snmpd    ### Ubuntu/Debian
sudo sed -i 's/OPTIONS=.*/OPTIONS="-LS0-5d"/' /etc/sysconfig/snmpd    ### CentOS/RHEL

## ------------------| Restart and enable SNMP
sudo systemctl restart snmpd
sudo systemctl enable snmpd

## ------------------| Configure SNMPv3 
###  Create SNMPv3 User
sudo net-snmp-create-v3-user -ro -A "authPassword" -X "privPassword" -a SHA -x AES snmpuser
### Add to /etc/snmp/snmpd.conf
sudo bash -c 'echo "rouser snmpuser authPriv" >> /etc/snmp/snmpd.conf'
### Restart SNMP Service
sudo systemctl restart snmpd
### Test SNMPv3
snmpwalk -v3 -u snmpuser -a SHA -A "authPassword" -x AES -X "privPassword" <device-ip> .1.3.6.1.2.1.1.1.0

02. Enumerations

• Nmap

## ------------------| Nmap General
sudo nmap -sU --open -p 161 $IP                                                                    ## Check if SNMP port (UDP 161) is open
sudo nmap -sU -p 161 -Pn -n -T4 -v --script=snmp-info --script-args=community=public $IP           ## Enumerate general SNMP information
sudo nmap -sU -p 161 -Pn -n -T4 -v --script=snmp-interfaces --script-args=community=public $IP     ## List network interfaces via SNMP
sudo nmap -sU -p 161 -Pn -n -T4 -v --script=snmp-netstat --script-args=community=public $IP        ## Retrieve netstat info via SNMP
sudo nmap -sU -p 161 -Pn -n -T4 -v --script=snmp-processes --script-args=community=public $IP      ## List running processes via SNMP
sudo nmap -sU -p 161 -Pn -n -T4 -v --script=snmp-sysdescr --script-args=community=public $IP       ## Get system description from SNMP
sudo nmap -sU -p 161 -Pn -n -T4 -v --script=snmp-hh3c-logins --script-args=community=public $IP    ## Extract Huawei login info via SNMP
sudo nmap -sU -p 161 -Pn -n -T4 -v --script=snmp-ios-config --script-args=community=public $IP     ## Attempt to download Cisco IOS config via SNMP
sudo nmap -sU -p 161 -Pn -n -T4 -v --script="snmp-* and not snmp-brute" --script-args=community=public $IP    ## Run all SNMP-related scripts

## ------------------| Special Nmap for Windows
sudo nmap -sU -p 161 -Pn -n -T4 -v --script=snmp-win32-services --script-args=community=public $IP ## List Windows services via SNMP
sudo nmap -sU -p 161 -Pn -n -T4 -v --script=snmp-win32-shares --script-args=community=public $IP   ## List Windows shares via SNMP
sudo nmap -sU -p 161 -Pn -n -T4 -v --script=snmp-win32-software --script-args=community=public $IP ## List installed Windows software via SNMP
sudo nmap -sU -p 161 -Pn -n -T4 -v --script=snmp-win32-users --script-args=community=public $IP    ## List Windows user accounts via SNMP

• Community Strings Brute-force

## ------------------| Common Community Strings
public
internal
private
manager
backup

## ------------------| Nmap
sudo nmap -sU -p 161 -Pn -n -T4 -v --script=snmp-brute --script-args="snmp-brute.communitiesdb=/usr/share/seclists/Discovery/SNMP/snmp.txt" $IP
sudo nmap -sU -p 161 -Pn -n -T4 -v --script=snmp-brute --script-args="snmp-brute.communitiesdb=/usr/share/seclists/Discovery/SNMP/common-snmp-community-strings.txt" $IP

## ------------------| Hydra
hydra -P /usr/share/seclists/Discovery/SNMP/snmp.txt -v $IP snmp
hydra -P /usr/share/seclists/Discovery/SNMP/common-snmp-community-strings.txt -v $IP snmp

## ------------------| OneSixtyOne
onesixtyone -c dict.txt -i iplist.txt
onesixtyone -c /usr/share/seclists/Discovery/SNMP/snmp.txt $IP
onesixtyone -c /usr/share/seclists/Discovery/SNMP/common-snmp-community-strings-onesixtyone.txt $IP
#### wget https://raw.githubusercontent.com/trailofbits/onesixtyone/master/dict.txt

## ------------------| SNMP-Brute
wget https://raw.githubusercontent.com/SECFORCE/SNMP-Brute/master/snmpbrute.py
python3 snmpbrute.py -t $IP
python3 snmpbrute.py -a -t $IP
python3 snmpbrute.py --sploitego -t $IP
python3 snmpbrute.py -f /usr/share/seclists/Discovery/SNMP/snmp.txt -t $IP
python3 snmpbrute.py -f /usr/share/seclists/Discovery/SNMP/common-snmp-community-strings.txt -t $IP

• Basic Enum

## ------------------| To read snmpwalk output as human readable
apt-get install snmp-mibs-downloader -y
cat /etc/snmp/snmp.conf
## Comment 👉mibs :👈 this

### First get the correct commiunity string from onesixtyone
## ------------------| Basic checks
snmpenum $IP public linux.txt        # Use this for Linux, then move in to snmpwalk !!
snmpenum $IP public windows.txt      # Use this for Windows, then move in to snmpwalk !!
snmp-check $IP -c public
snmpwalk -c public -v1 $IP
snmpwalk -c public -v2c $IP
snmpwalk -c internal -v2c $IP | tee snmpwalk.out
snmpbulkwalk -c public -v2c $IP | tee snmpbulkwalk.out
snmpbulkwalk -Cr1000 -c public -v2c $IP | tee snmpbulkwalk.out

## ------------------| Analyze / Grep
grep -oP '::.*?\.' snmpwalk.out | sort | uniq -c | sort -n

• SNMP OIDs (Object Identifiers)

## ------------------| Common for both OS
snmpwalk -c public -v1 $IP -Ovq HOST-RESOURCES-MIB::hrSWRunParameters    ## Get running services with args
snmpwalk -c public -v1 $IP .1.3.6.1.2.1.1.5.0           ## System Name (Hostname)
snmpwalk -c public -v1 $IP .1.3.6.1.2.1.1.1.0           ## System Description (OS, hardware, version)
snmpwalk -c public -v1 $IP .1.3.6.1.2.1.25.4.2.1.2      ## Running Processes (Process names)
snmpwalk -c public -v1 $IP .1.3.6.1.2.1.25.4.2.1.4      ## Process Paths (Executable paths)
snmpwalk -c public -v1 $IP .1.3.6.1.2.1.25.1.6.0        ## System Processes (Running process count)
snmpwalk -c public -v1 $IP .1.3.6.1.2.1.25.6.3.1.2      ## Installed Software (Software inventory)
snmpwalk -c public -v1 $IP .1.3.6.1.2.1.1.7.0           ## System Services (Running services summary)
snmpwalk -c public -v1 $IP .1.3.6.1.2.1.25.4.2.1.5      ## Process Arguments (Command-line arguments)
snmpwalk -c public -v1 $IP .1.3.6.1.2.1.25.2.3.1.4      ## Storage Units (Disk/partition details)
snmpwalk -c public -v1 $IP .1.3.6.1.2.1.6.13.1.3        ## Open TCP Ports (Active connections)
snmpwalk -c public -v1 $IP .1.3.6.1.2.1.2.2.1.2         ## Network Interfaces (Interface names/descriptions)
snmpwalk -c public -v1 $IP .1.3.6.1.2.1.2.2.1.6         ## Network Interface MAC Addresses
snmpwalk -c public -v1 $IP .1.3.6.1.2.1.4.22.1.2        ## ARP Table (IP-to-MAC mappings)
snmpwalk -c public -v1 $IP .1.3.6.1.2.1.25.3.2.1.3      ## Get hardware device names
snmpwalk -c public -v1 $IP .1.3.6.1.2.1.1.6.0           ## System Location

## ------------------| Get ipAddressTable
snmpwalk -c public -v1 $IP 1.3.6.1.2.1.4.34.1.3 
snmpwalk -c public -v2c $IP 1.3.6.1.2.1.4.34.1.3 
### IPV6
snmpwalk -v2c -c public $IP ipAddressIfIndex.ipv6 | cut -d'"' -f2 | grep 'de:ad' | sed -E 's/(.{2}):(.{2})/\1\2/g'
### Using Enyx
## wget https://raw.githubusercontent.com/trickster0/Enyx/master/enyx.py
## cat /etc/snmp/snmp.conf
## Unomment 👉mibs :👈 this
python enyx.py 2c public 10.10.10.20

## ------------------| Special for Windows
snmpwalk -c public -v1 $IP .1.3.6.1.4.1.77.1.2.25       ## User Accounts (Local user accounts)
snmpwalk -c public -v1 $IP .1.3.6.1.4.1.77.1.2.3.1.1    ## Domain Information (Domain membership details)
snmpwalk -c public -v1 $IP .1.3.6.1.4.1.77.1.2.2        ## Windows Groups (Local group accounts)
snmpwalk -c public -v1 $IP .1.3.6.1.4.1.77.1.2.27       ## Windows Shares (Shared folders/drives)
snmpwalk -c public -v1 $IP .1.3.6.1.4.1.77.1.2.1        ## Windows Services (Detailed service information)
snmpwalk -c public -v1 $IP .1.3.6.1.4.1.77.1.2.14       ## Installed Patches (Windows update details)
snmpwalk -c public -v1 $IP .1.3.6.1.2.1.25.6.3.1.4      ## Get Windows software install location
snmpwalk -c public -v1 $IP .1.3.6.1.2.1.25.6.3.1.5      ## Get Windows software version

## ------------------| Special for Linux
snmpwalk -c public -v1 $IP .1.3.6.1.4.1.2021.4.3.0      ## Total RAM (Memory size)
snmpwalk -c public -v1 $IP .1.3.6.1.4.1.2021.4.11.0     ## Free RAM (Available memory)
snmpwalk -c public -v1 $IP .1.3.6.1.4.1.2021.11.9.0     ## CPU Load (1-minute average)
snmpwalk -c public -v1 $IP .1.3.6.1.4.1.2021.10.1.3.1   ## CPU Load (Detailed 1-minute load)
snmpwalk -c public -v1 $IP .1.3.6.1.4.1.2021.9.1.2      ## Mounted Filesystems (Mount points)
snmpwalk -c public -v1 $IP .1.3.6.1.4.1.2021.9.1.7      ## Disk Usage (Free space per filesystem)
snmpwalk -c public -v1 $IP .1.3.6.1.4.1.2021.8.1.101    ## Custom Scripts (If extended via /etc/snmp/snmpd.conf)
snmpwalk -c public -v1 $IP 1.3.6.1.2.1.25.3.8.1.2       ## Get mounted filesystem paths
snmpwalk -c public -v1 $IP 1.3.6.1.2.1.25.3.2.1.5       ## Get device types
snmpwalk -c public -v1 $IP 1.3.6.1.2.1.1.3.0            ## Get system uptime
snmpwalk -c public -v1 $IP 1.3.6.1.2.1.25.3.3.1.2       ## Get CPU load