Port 445: SMB
Port 445 is modern SMB, the protocol behind Windows file and printer sharing. It is powerful and heavily targeted, so it should never be exposed to the internet.
| Port number | 445 |
|---|---|
| Service | SMB / CIFS file sharing |
| Protocol | TCP |
| Category | Windows |
| Default encryption | No |
How do I check whether port 445 is open?
Port 445 carries TCP, so a connection either completes its handshake or it does not, which makes the check definitive.
| Question | Command | What to know |
|---|---|---|
| Is it open on a remote host? | nc -vz example.com 445 | A TCP handshake either completes or it does not, so netcat gives a definitive answer in one line. |
| Same check on Windows | Test-NetConnection example.com -Port 445 | Built into PowerShell. TcpTestSucceeded in the output is the answer; telnet is not installed by default on modern Windows. |
| What is listening locally? | ss -tlnp | grep ':445 ' | Lists the process bound to port 445 on Linux. On macOS use lsof -nP -iTCP:445 -sTCP:LISTEN, on Windows netstat -ano | findstr :445 |
Replace example.com with the host you are testing. A blocked port and a port with nothing listening on it look identical from the outside, so if a service should be running, check locally before blaming the firewall.
Frequently asked questions
What is port 445 used for?
Port 445 is modern SMB, the protocol behind Windows file and printer sharing. It is powerful and heavily targeted, so it should never be exposed to the internet.
Is port 445 TCP or UDP?
Port 445 (SMB) uses TCP.
Is port 445 secure?
Port 445 is not encrypted by default. Where possible, use an encrypted alternative or tunnel it over TLS or a VPN.
Should I open port 445 on my firewall?
Only if you specifically need SMB. Expose it to the smallest set of trusted sources, and never open database or Windows-service ports to the whole internet.