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Port 445 – SMB (Server Message Block)

Service:

smbd ,
srvsvc ,
Windows File Sharing

Protocol:

TCP

Port:

445

Used for:

File sharing, printer access, and Windows domain operations

Why It’s Open

Port 445 is critical in Windows networks for everything from file shares to domain authentication. It replaced NetBIOS-based SMB traffic.

Common Risks

  • EternalBlue & WannaCry: SMBv1-based exploits.
  • SMB Relay & Man-in-the-Middle: NTLM hash theft.
  • Unauthorized Access: Misconfigured shares and ACLs.

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Enumeration & Testing

Nmap discovery

Terminal window
nmap -p 445 --script smb-enum-shares,smb-os-discovery


smbclient -L /// -N

What to Look For

CheckpointWhat it means
SMBv1 supportLegacy and vulnerable
Guest access enabledUnauthenticated share access
Null sessionsInfo disclosure risk

Known Exploits

  1. CVE-2017-0144 EternalBlue exploit allows remote attackers to execute arbitrary code via crafted packets. 🔗 NVD Entry

  2. CVE-2020-0796 SMBGhost vulnerability enables remote code execution in SMBv3. 🔗 NVD Entry

Mitigation

  • Disable SMBv1 and enforce SMB signing.
  • Require strong authentication.
  • Segment and audit shares.
  • Use Group Policy to limit anonymous access.

Real-World Example

SMB over 445 was the main vector for the WannaCry ransomware outbreak in 2017, causing billions in damages globally.

TL;DR

  • Service: SMB (File and Printer Sharing)
  • Default Port: 445/TCP
  • Risks: Remote code execution, lateral movement
  • Mitigation: Apply patches, disable SMBv1, restrict access