Networking Protocols Explained | CyberSecurity

Shakhawat Hossain - 0xShakhawat
7 min readJun 4, 2022
Networking Protocols Explained by 0xShakhawat
Networking Protocols


FTP-File Transfer Protocol: Port 21

This is sometimes called the command or control port by default. Then the client makes another connection to the server over port 20 for file transfers to take place. The administrator can change the default port for sending commands and files over FTP.

The FTP protocol typically uses port 21 as its main means of communication. An FTP server will listen for client connections on port 21. FTP clients will then connect to the FTP server on port 21 and initiate a conversation. This main connection is called the Control Connection or Command Connection.

SSH-Secure Shell: Port 22

SSH or Secure Shell is a network communication protocol that enables two computers to communicate (c.f http or hypertext transfer protocol, which is the protocol used to transfer hypertext such as web pages) and share data.

The port is used for Secure Shell (SSH) communication and allows remote administration access to the VM. In general, traffic is encrypted using password authentication.

Telnet — Port 23

Port 23 is typically used by the Telnet protocol. Telnet commonly provides remote access to a variety of communications systems. Telnet is also often used for remote maintenance of many networking communications devices including routers and switches.

A Telnet client program presents a terminal-like window to its user and, when given a remote IP and optional port (port 23 is the default) attempts to connect to the remotely located machine to initiate a Telnet session. Since anyone with access to the network — or Internet — can access the Telnet server running in a device, the user must typically log onto the device with a user name and password.

SMTP-Simple Mail Transfer Protocol: Port 25

The Simple Mail Transfer Protocol is an internet standard communication protocol for electronic mail transmission. Mail servers and other message transfer agents use SMTP to send and receive mail messages.

Port 25 is the original standard email SMTP port and the oldest, since it first debuted in 1982. Today, the Internet Assigned Numbers Authority (IANA), the group responsible for maintaining the internet addressing scheme, still recognizes port 25 as the standard, default SMTP port.

DNS Domain Naming System (or Service): Port 53

The Domain Name Service (DNS) uses UDP port 53 and TCP port 53. Your storage system does not typically listen on these ports because it does not run a domain name server. However, if DNS is enabled on your storage system, it makes outgoing connections using UDP port 53 for host name and IP address lookups.

The DNS uses TCP Port 53 for zone transfers, for maintaining coherence between the DNS database and the server. The UDP protocol is used when a client sends a query to the DNS server. The TCP protocol should not be used for queries as it gives a lot of information, which is useful to attackers.

HTTP-Hypertext Transfer Protocol: Port 80

Short for Hypertext Transfer Protocol, HTTP is a set of standards that allow users of the World Wide Web to exchange information found on web pages. When accessing any web page entering http:// in front of the address tells the browser to communicate over HTTP.

PORT 80 is the default port used by Hypertext Transfer Protocol. When you visit a website, it serves your browser information over port 80. Unfortunately, because it’s so popular, it is also used by a number of viruses.

POP3-Post Office Protocol: Port 110

POP3 Post Office Protocol version 3 (POP3) is one of the two protocols that receive e-mail from SMTP servers. POP3 uses TCP port 110. Most e-mail clients use this protocol, although some use IMAP4.

The server starts POP3 service by listening on TCP port 110. When a client wishes to use POP3 for email retrieval, it establishes a TCP connection with the server host. Once this connection is established, the POP3 server sends a greeting. At this point, the session enters the authorization state.

IMAP Internet Message Access Protocol: Port 143.

IMAP typically uses ports 143 and 993. Port 143 is non-encrypted (unsecure) and is the default port, while port 993 is the encrypted port (secure). On no account should port 143 be open and accessible to the outside world. It is an unsecure port and can be a gateway to digital eavesdropping and attacks.
IMAP being used by hackers to bypass multi-factor authentication, says report. Multi-factor authentication is touted by experts as one of the best ways to protect email against brute force attacks and spear phishing lures on credentials.

HTTPS-HTTP Secure Port 443

HTTPS is secure and is on port 443, while HTTP is unsecured and available on port 80. Information that travels on the port 443 is encrypted using Secure Sockets Layer (SSL) or its new version, Transport Layer Security (TLS) and hence safer.

RDP-Remote Desktop Protocol: Port 3389

Remote Desktop Protocol (RDP) is a Microsoft proprietary protocol that enables remote connections to other computers, typically over TCP port 3389. It provides network access for a remote user over an encrypted channel.

TCP-Transmission Control Protocol

Transmission Control Protocol (TCP) is a standard that defines how to establish and maintain a network conversation by which applications can exchange data. TCP works with the Internet Protocol (IP), which defines how computers send packets of data to each other.

UDP-User Datagram Protocol

In computer networking, the User Datagram Protocol is one of the core members of the Internet protocol suite. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol network.

ARP Address Resolution Protocol

Address Resolution Protocol (ARP) is a protocol or procedure that connects an ever-changing Internet Protocol (IP) address to a fixed physical machine address, also known as a media access control (MAC) address, in a local-area network (LAN).

RARP Reverse ARP

The Reverse Address Resolution Protocol is an obsolete computer communication protocol used by a client computer to request its Internet Protocol address from a computer network, when all it has available is its link layer or hardware address, such as a MAC address.

DHCP-Dynamic Host Configuration Protocol: Server Port 67, Client Port 68

UDP port number 67 is the destination port of a server, and UDP port number 68 is used by the client. DHCP operations fall into four phases: server discovery, IP lease offer, IP lease request, and IP lease acknowledgement. These stages are often abbreviated as DORA for discovery, offer, request, and acknowledgement.

MTP-Media Transfert Protocol

The Media Transfer Protocol is an extension to the Picture Transfer Protocol communications protocol that allows media files to be transferred automatically to and from portable devices.

SFTP Secure File Transfer Protocol

Secure File Transfer Protocol, also SFTP, is a network protocol for transferring, accessing, and managing files between machines over an encrypted connection. It builds on File Transfer Protocol (FTP) software and uses the SSH (secure shell) protocol to transfer.

SSL-Secure Socket Layer

A Secure Sockets Layer certificate (SSL certificate) is a small data file installed on a Web server that allows for a secure connection between the server and a Web browser.

TLS Transport Layer Security

Transport Layer Security, the successor of the now-deprecated Secure Sockets Layer, is a cryptographic protocol designed to provide communications security over a computer network.

E6 Ethernet globalization protocols

NTP-Network time protocol

The Network Time Protocol is a networking protocol for clock synchronization between computer systems over packet-switched, variable-latency data networks. In operation since before 1985, NTP is one of the oldest Internet protocols in current use. NTP was designed by David L. Mills of the University of Delaware

PPP-Point to Point Protocol

Point-to-Point Protocol (PPP) is a TCP/IP protocol that is used to connect one computer system to another. Computers use PPP to communicate over the telephone network or the Internet. A PPP connection exists when two systems physically connect through a telephone line. You can use PPP to connect one system to another

NNTP-Network News Transfer Protocol

The Network News Transfer Protocol is an application protocol used for transporting Usenet news articles between news servers, and for reading/posting articles by the end user client applications.

QOTD-Quote Of The Day

Quote of the Day is a simple protocol that is used to deliver daily quotes. Although its usage is almost nonexistent these days, there are still a few public servers. The protocol is defined by RFC 865. According to the RFC, a QOTD server is run on port 17 for TCP and UDP connections.

Bitcoin Protocol — Protocol for Bitcoin transactions and transfers on the web

The bitcoin network is a peer-to-peer payment network that operates on a cryptographic protocol. Users send and receive bitcoins, the units of currency, by broadcasting digitally signed messages to the network using bitcoin cryptocurrency wallet software.

ICMP Internet Control Message Protocol

Internet Control Message Protocol (ICMP) is used for reporting errors and performing network diagnostics. In the error reporting process, ICMP sends messages from the receiver to the sender when data does not come though as it should.

IGMP-Internet Group Management Protocol

The Internet Group Management Protocol is a communications protocol used by hosts and adjacent routers on IPv4 networks to establish multicast group memberships. IGMP is an integral part of IP multicast and allows the network to direct multicast transmissions only to hosts that have requested them.

GGP Gateway-to-Gateway Protocol

The Gateway-to-Gateway Protocol is an obsolete protocol defined for routing datagrams between Internet gateways. It was first outlined in 1982. The Gateway-to-Gateway Protocol was designed as an Internet Protocol datagram service similar to the Transmission Control Protocol and the User Datagram Protocol.