Special Credit to Hamza Shah | LinkedIN

This is not an exhaustive list and should only serve as a gentle reminder

Web Services

Port(s)ProtocolDescription
80/443HTTP/HTTPSStandard web traffic
8000/8080/8443HTTP/HTTPSAlternative web ports frequently seen

File Transfer

PortProtocolDescription
21FTPFile Transfer Protocol
22SSHSecure Shell
445SMBServer Message Block

Directory Services

PortProtocolDescription
389/636LDAP/LDAPSLightweight Directory Access Protocol
88KerberosNetwork authentication protocol

Database Services

PortProtocolDescription
1433MS SQLMicrosoft SQL Server
3306MySQLMySQL Database
5432PostgreSQLPostgreSQL Database

Email - Messaging

PortProtocolDescription
25SMTPSimple Mail Transfer Protocol
110/995POP3/POP3SPost Office Protocol (secure)
143/993IMAP/IMAPSInternet Message Access Protocol (secure)

Management Protocols

PortProtocolDescription
161/162SNMPSimple Network Management Protocol (UDP)
3389RDPRemote Desktop Protocol
5985/5986WinRMWindows Remote Management

Other Important Services

PortProtocolDescription
53DNSDomain Name System
135MSRPCMicrosoft Remote Procedure Call
139NetBIOSNetwork Basic Input/Output System
1080SOCKSSOCKS Proxy
23TelnetTelnet Protocol