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IPFYI
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81

HTTP Alternate

Medium Risk

TCP — Web

Port Overview

Port Number 81
Service Name HTTP Alternate
Transport Protocol TCP
Category Web
Security Risk Medium
Port Range Well-Known (0-1023)

What is Port 81?

Port 81 is an unofficial alternate HTTP port used when port 80 is unavailable or blocked, commonly seen on home routers, development servers, and some commercial web appliances. Publicly exposed port 81 web services are frequently targeted by automated vulnerability scanners.

TCP Web Commonly Used

Security Considerations

Port 81 (HTTP Alternate) is classified as medium risk. While this service is commonly exposed, consider using encrypted alternatives where available.

Recommendation: Keep the service updated. Monitor logs for unusual activity.

Related Ports — Web

70 Gopher 80 HTTP 280 http-mgmt 443 HTTPS 808 CCProxy HTTP 843 Flash Policy 901 SWAT 1001 webpush
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