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Port 445Microsoft-DS / SMB

Port 445 is primarily used for Microsoft Directory Services (Microsoft-DS), supporting file sharing, printer sharing, and access to Active Directory via the Server Message Block (SMB) protocol over TCP. It has replaced older NetBIOS ports, facilitating more efficient direct communication, and is widely deployed across Windows environments for seamless network resource access..

inFile TransferNetwork ServicesSystem
transport
tcp

single transport

in transit
cleartext

payload readable on path

assignment
official

registered with iana

risk
5/10

caution

lookups
22,289

rank 96 of 993 · top 10%

1 other service is registered on port 445. compare all 2 →

Technical Details

what runs on :445

Port 445 is designated for direct hosting of the Server Message Block (SMB) protocol over TCP/IP, superseding older implementations that relied on NetBIOS over TCP (ports 137-139). This facilitates network file and printer sharing, as well as Active Directory operations like authentication and replication. Microsoft's implementation of SMB on port 445 enables seamless access to resources across Windows networks without the overhead of legacy protocols.

Technically, SMB is an application-layer network protocol primarily designed to provide shared access to files and printers. The shift to direct hosting over port 445 modernized communication by reducing protocol complexity, improving performance, and enabling better integration with other Windows network services. Active Directory heavily relies on SMB for various directory-related operations, making port 445 vital to Windows domain functionality.

Beyond Windows, some UNIX-like systems via Samba have implemented SMB compatibility, enhancing interoperability in mixed-OS environments. However, this broad utility also means the port is widely exposed and targeted if improperly secured. Managing access to port 445 is critical in enterprise networks to maintain both operability and security.

Security Information

exposure of :445

risk score

5/ 10caution

worth attention. how exposed you are depends on configuration — don't leave it reachable from the internet without a reason.

file transfer averages 4.1 across 114 ports — this one sits 0.9 above.

in transit

cleartext

credentials and payloads are readable by anyone on path

assignment

official

registered with iana for this service — scanners fingerprint it by number

reachable over

tcp

every listening transport is another surface to filter at the edge

security overview

Common Vulnerabilities:

  • SMB vulnerabilities like EternalBlue exploited by WannaCry ransomware rely on flaws when port 445 is exposed.
  • Lack of encryption or signing allows man-in-the-middle attacks, data interception, or credential theft.
  • Insecurely configured shares can lead to unauthorized access and lateral movement by attackers.
  • Exposure over the Internet significantly increases susceptibility to automated brute-force scans, worm propagation, and zero-day exploits.

Common Mitigations:

  • Block inbound and outbound port 445 traffic at the network perimeter, only allowing trusted internal communication.
  • Regularly patch and update SMB services to address vulnerabilities.
  • Enable SMB signing and encryption where possible, especially on SMBv3 and above.
  • Disable legacy SMB versions (SMBv1) to reduce the attack surface.
  • Implement network segmentation and access control lists (ACLs) to limit unauthorized access.
  • Use strong authentication mechanisms, including multi-factor authentication for administrative access.
  • Monitor and log SMB activity for anomaly detection and incident response.

Related Ports

all 114 in file transfer →

the 8 most looked-up other ports in file transfer — 114 ports carry that label.

portservicerisk
:9080Groove RPCcaution
:17500Dropbox LAN Synccaution
:548Apple Filing Protocolcaution
:7000Vuze HTTPS Trackercaution
:1337PowerFolder P2Pcaution
:9001SharePoint Authoringcaution
:8080FilePhile Relaycaution
:1337WASTE Encrypted Sharingcaution

risk mix of the 8 listed

  • caution100%

1 of 8 encrypted