The 8 Most Vulnerable Ports to Check When Pentesting

Scanning ports is a crucial a part of penetration testing. It means that you can establish and exploit vulnerabilities in web sites, cell functions, or techniques. As a penetration tester or moral hacker, it’s important you realize the best and most susceptible ports to assault when finishing up a take a look at.

So what really are open ports? And which ports are most susceptible?

What Is a Penetration Take a look at?

A penetration take a look at is a type of moral hacking that entails finishing up approved simulated cybersecurity assaults on web sites, cell functions, networks, and techniques to find vulnerabilities on them utilizing cybersecurity methods and instruments. That is executed to judge the safety of the system in query.

What Are Ports?

A port is a digital array utilized by computer systems to speak with different computer systems over a community. A port can also be known as the quantity assigned to a particular community protocol. A community protocol is a algorithm that decide how units transmit knowledge backward and forward on a community.

The 2 most typical varieties of community protocols are the Transmission Management Protocol (TCP) and the Person Datagram Protocol (UDP).

Transmission Management Protocols

TCP is a communication commonplace that permits units to ship and obtain data securely and orderly over a community. It does this by establishing a connection from the consumer laptop to the server or designated laptop, after which sending packets of knowledge over the community. TCP works hand in hand with the web protocol to attach computer systems over the web.


Person Datagram Protocols

UDP works very very like TCP, solely it doesn’t set up a connection earlier than transferring data. The UDP is quicker than the TCP as a result of it skips the establishing connection step and simply transfers data to the goal laptop over a community. This makes it unreliable and fewer safe.

Find out how to Examine for Open Ports

An open port is a TCP or UDP port that accepts connections or packets of knowledge. If a port rejects connections or packets of knowledge, then it’s known as a closed port. Open ports are crucial for community visitors throughout the web.

To examine for open ports, all you want is the goal IP deal with and a port scanner. There are numerous free port scanners and penetration testing instruments that can be utilized each on the CLI and the GUI. The preferred port scanner is Nmap, which is free, open-source, and straightforward to make use of. Should you’re unfamiliar with it, you possibly can discover ways to scan for open ports utilizing Nmap.

Are All Open Ports Weak?

Not essentially. Though a closed port is much less of a vulnerability in comparison with an open port, not all open ports are susceptible. Reasonably, the providers and applied sciences utilizing that port are liable to vulnerabilities. So, if the infrastructure behind a port is not safe, that port is liable to assault.

Weak Ports to Look Out For


There are over 130,000 TCP and UDP ports, but some are extra susceptible than others. In penetration testing, these ports are thought of low-hanging fruits, i.e. vulnerabilities which might be simple to use.

Many ports have recognized vulnerabilities that you could exploit after they come up within the scanning part of your penetration take a look at. Listed below are some frequent susceptible ports you should know.

1. FTP (20, 21)

FTP stands for File Switch Protocol. Port 20 and 21 are solely TCP ports used to permit customers to ship and to obtain recordsdata from a server to their private computer systems.

The FTP port is insecure and outdated and could be exploited utilizing:

  • Nameless authentication. You’ll be able to log into the FTP port with each username and password set to “nameless”.
  • Cross-Website Scripting.
  • Brute-forcing passwords.
  • Listing traversal assaults.

2. SSH (22)

SSH stands for Safe Shell. It’s a TCP port used to make sure safe distant entry to servers. You’ll be able to exploit the SSH port by brute-forcing SSH credentials or utilizing a non-public key to achieve entry to the goal system.

3. SMB (139, 137, 445)

SMB stands for Server Message Block. It’s a communication protocol created by Microsoft to supply sharing entry of recordsdata and printers throughout a community. When enumerating the SMB port, discover the SMB model, after which you possibly can seek for an exploit on the web, Searchsploit, or Metasploit.

The SMB port could possibly be exploited utilizing the EternalBlue vulnerability, brute forcing SMB login credentials, exploiting the SMB port utilizing NTLM Seize, and connecting to SMB utilizing PSexec.

An instance of an SMB vulnerability is the Wannacry vulnerability that runs on EternalBlue

4. DNS (53)

DNS stands for Area Identify System. It’s each a TCP and UDP port used for transfers and queries respectively. One frequent exploit on the DNS ports is the Distributed Denial of Service (DDoS) assault.

5. HTTP / HTTPS (443, 80, 8080, 8443)

HTTP stands for HyperText Switch Protocol, whereas HTTPS stands for HyperText Switch Protocol Safe (which is the safer model of HTTP). These are the preferred and extensively used protocols on the web, and as such are liable to many vulnerabilities. They’re susceptible to SQL injections, cross-site scripting, cross-site request forgery, and so forth

6. Telnet (23)

The Telnet protocol is a TCP protocol that allows a consumer to hook up with distant computer systems over the web. The Telnet port has lengthy been changed by SSH, however it’s nonetheless utilized by some web sites at the moment. It’s outdated, insecure, and susceptible to malware. Telnet is susceptible to spoofing, credential sniffing, and credential brute-forcing.

7. SMTP (25)

SMTP stands for Easy Mail Switch Protocol. It’s a TCP port used for sending and receiving mails. It may be susceptible to mail spamming and spoofing if not well-secured.

8. TFTP (69)

TFTP stands for Trivial File Switch Protocol. It is a UDP port used to ship and obtain recordsdata between a consumer and a server over a community. TFTP is a simplified model of the file switch protocol. As a result of it’s a UDP port, it doesn’t require authentication, which makes it quicker but much less safe.

It may be exploited utilizing password spraying and unauthorized entry, and Denial of Service (DoS) assaults.

Port Scanning as a Pentester

As a penetration tester or moral hacking, the significance of port scanning can’t be overemphasized. Port scanning lets you collect details about a given goal, know the providers operating behind particular ports, and the vulnerabilities connected to them.

Now that you realize essentially the most susceptible ports on the web, you need to use this data to carry out pentests. Good luck!

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