Port 445 — SMB

TCP well-known

What runs on port 445

Windows file and printer sharing.

Security considerations

Should never be reachable from the internet. This is the port WannaCry and NotPetya spread over.

Checking whether something is listening

# Linux / macOS — what is bound to the port
sudo lsof -i :445
sudo ss -lntp | grep :445

# Windows
netstat -ano | findstr :445
Get-NetTCPConnection -LocalPort 445

# is it reachable from outside?
nc -zv example.com 445
curl -v telnet://example.com:445

Freeing the port

# find the process, then stop it
sudo lsof -ti :445 | xargs kill        # Linux / macOS
netstat -ano | findstr :445            # note the PID, then:
taskkill /PID <pid> /F                    # Windows

Should this port be open to the internet?

No. Port 445 should never be reachable from a public address. Bind it to localhost or a private network, and reach it through a VPN or bastion host if remote access is genuinely needed. Internet-wide scanners find newly exposed instances of this service within minutes.

Quick reference

Frequently asked questions

Other common ports

• Port 20 — FTP data
• Port 21 — FTP control
• Port 22 — SSH / SFTP
• Port 23 — Telnet
• Port 25 — SMTP
• Port 53 — DNS
• Port 67 — DHCP server
• Port 68 — DHCP client
• Port 69 — TFTP
• Port 80 — HTTP
• Port 110 — POP3
• Port 123 — NTP
• Port 143 — IMAP
• Port 161 — SNMP
• Port 389 — LDAP
• Port 443 — HTTPS
• Port 465 — SMTPS
• Port 514 — Syslog

All port numbers