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// IoT & industrial (ICS)

Port 47808: BACnet

Building automation (HVAC, access control, lighting).

47808

How BACnet works

IoT & industrial (ICS)
controllerPLCWritePropertyno authentication controllerPLCWritePropertyno authentication

A controller sends commands to an industrial device on port 47808, which acts on the physical process. It travels in clear text: anyone on the path can read it.

Transport
UDP · TCP
Exposure risk
9/10 critical if reachable from the Internet
Encryption
Clear textreadable on the network
IANA status
Assigned1 registered service
Range
Registered (1024-49151)
Category
IoT & industrial (ICS)
01 Security

Is port 47808 dangerous?

Common attacks and weaknesses

  • Unauthenticated control of building systems exposed on the Internet.

How to secure it

  • Keep building automation off the Internet; use BACnet/SC where possible.
02 Registry

IANA registry entries for port 47808

ServicePortTransportDescriptionReferenceUpdated
bacnet 47808 TCP, UDP Building Automation and Control Networks - 2011-02-10

// source: IANA service name and port number registry

03 Check it

Which program uses port 47808, and is it reachable?

Linux

sudo ss -ltnup 'sport = :47808'      # process listening on 47808
sudo lsof -nP -i :47808

macOS

sudo lsof -nP -i :47808

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 47808 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 47808
netstat -ano | findstr :47808

From another machine

nmap -p 47808 -sV <host>
sudo nmap -sU -p 47808 <host>
nc -zv <host> 47808

Block it in the firewall

sudo ufw deny 47808/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 47808" -Direction Inbound -LocalPort 47808 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 47808 used for?

Building automation (HVAC, access control, lighting).

Is port 47808 TCP or UDP?

Port 47808 is registered for UDP and TCP. In practice the service mostly uses UDP.

Is it safe to open port 47808?

It is rated 9/10 (critical) when exposed to the Internet. Unauthenticated control of building systems exposed on the Internet. Keep building automation off the Internet; use BACnet/SC where possible.

How do I check if port 47808 is open?

On Linux run "ss -ltnup 'sport = :47808'", on macOS "lsof -nP -i :47808", and on Windows "netstat -ano | findstr :47808" to see the local process. From another machine, "nmap -p 47808 <host>" shows whether it is reachable.

05 Related
:1883 MQTT tcp · udp · high risk :8883 MQTT over TLS tcp · udp · moderate risk :502 Modbus TCP tcp · udp · critical risk :102 Siemens S7 (ISO-TSAP) tcp · udp · critical risk :20000 DNP3 tcp · udp · sctp · critical risk :44818 EtherNet/IP tcp · udp · critical risk :802 Modbus Application Protocol Secure tcp · udp :2221 EtherNet/IP over TLS tcp · udp

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