Ethical Hacking Module 2: TCP Ports to Remember

Ports 20 and 21 File Transfer Protocol

Has been around as long as the Internet. Was the standard for moving and copying large files and is still used today albeit less because of HTTP. One port is used for data transfer and the other is used for control. This protocol also does not use encryption.

Port 22 Secure Shell

Uses encryption and authentication to create a secure channel over an unsecure network.

• used to secure logons, file transfers, and port forwarding.

• FTP is unsecure, but you can make it secure using this type of channel.

• FTP using this port is known as SFTP.

Port 25 Simple Mail Transfer Protocol

Email servers listen on this port. If you attempt to send email to a remote user, your workstation connects this port on a mail server.

Port 53 Domain Name System

If a server on your network uses DNS, it’s using this port. Most networks require a DNS server so that users can connect to websites with URLs instead of IP addresses. When a user enters a URL, such as google, the DNS server resolves the name to an IP address. The DNS server might be internal to the company, or each computer might be configured to point to the IP address of a DNS server that’s serviced by the company’s ISP.

Port 69 Trivial File Transfer Protocol

Many network engineers use this service to transfer router and backup router configurations.

Port 80 HTTP

Most certification exams have a question about this port being used. This port is used when you connect to a web server. This is not secure, so most web servers use HTTPS (port 443).

Port 143 IMAP

Email clients use this port to retrieve email messages from a mail server over a TCP/IP connection.

Port 443 Secure Hypertext Transfer Protocol

Similar to port 80, this one is used when you connect to a web server. However, it typically is reserved for secure connections.

Port 993 IMAPS

IMAP over SSL/TLS uses this port. Connections using this port are secured, so it is preferred over the unsecured version IMAP, which uses port 143.

Port 110 Post Office Protocol 3

To retrieve email from a mail server, one option is to access port 110 using this protocol. An enhanced email retrieving protocol, IMAP4, is also available. It is still around, however, and is one of the most common email retrieval systems.

Port 119 Network News Transfer Protocol

This port is used to connect to a news server for us with newsgroups.

Port 135 Remote Procedure Call

This port, used by Microsoft RPC, is critical for the operation of Microsoft Exchange Server and Active Directory, avaliable in Windows 2000 Server and later.

Port 139 NetBIOS

This port is used by the Microsoft NetBIOS Session Service to share resources.

Port 143 Internet Message Access Protocol 4

IMAP4 uses this port to retrieve email.