What is the difference between insecure and secure ports in network security?

Table of Contents

• What Are Network Ports and Why Do They Matter?
• Insecure vs Secure Ports Table
• Why These Ports Matter in Real-World Security
• Real-World Example: University Network Misconfiguration
• Best Practices for Managing Insecure and Secure Ports in 2025
• Conclusion
• Frequently Asked Questions (FAQs)

In today's cybersecurity environment, understanding the difference between insecure and secure ports is crucial for protecting data in transit. Many data breaches and cyberattacks happen due to unencrypted communications across insecure ports, often overlooked by administrators and students new to network security.

This blog provides a simple, practical guide for understanding which ports are considered insecure and which are secure, complete with real-world use cases and best practices for 2025.

What Are Network Ports and Why Do They Matter?

Network ports act like channels that allow applications and services to communicate across networks. Each service typically uses a specific port number.

If a service runs on an insecure port, attackers can eavesdrop, perform man-in-the-middle attacks, or inject malicious data. By default, many legacy ports transmit information in plaintext without encryption.

Insecure vs Secure Ports Table

Why These Ports Matter in Real-World Security

• Telnet vs SSH: Many older devices still use Telnet for remote management. In 2025, using Telnet in any corporate network is considered a high-risk vulnerability. SSH is now the global standard.

• FTP vs SFTP: If a file transfer system uses FTP in industries like healthcare or finance, attackers could easily capture sensitive records. Switching to SFTP protects patient data and financial records.

• HTTP vs HTTPS: E-commerce platforms and banking websites must use HTTPS. HTTP leaves user login details, credit card numbers, and personal information exposed.

Real-World Example: University Network Misconfiguration

In 2024, a university's IT department left port 21 (FTP) open on public-facing servers. Hackers scanned for open FTP ports and managed to download internal student records. This breach highlighted why educational institutions must regularly audit for insecure ports.

Best Practices for Managing Insecure and Secure Ports in 2025

• Conduct Regular Port Scans: Use tools like Nmap to identify open ports and detect insecure services.

• Enforce Firewall Rules: Block known insecure ports like 21, 23, 25 (without TLS), and 80 on firewalls and routers.

• Migrate Legacy Systems: Move away from outdated services like Telnet and FTP.

• Implement DNS Over TLS (DoT): Protect domain queries from being monitored or tampered with.

• Always Use HTTPS: Ensure all websites, APIs, and services are served via HTTPS rather than HTTP.

• Educate IT Teams: Ensure security teams and IT students understand which ports require encryption.

Conclusion: Securing Your Network Starts with Ports

Understanding insecure versus secure ports is foundational knowledge for both cybersecurity students and enterprise IT teams. As attacks become more sophisticated, attackers actively look for misconfigured or outdated services running on insecure ports.

By prioritizing encrypted protocols and phasing out insecure ones, organizations significantly reduce their attack surface.

FAQs 

What are insecure ports in network security?

Insecure ports transmit data in plaintext without encryption, exposing sensitive information to interception and cyberattacks.

What are secure ports in network security?

Secure ports use encryption protocols like TLS or SSH to protect data while it is transmitted across a network.

Why is port 21 considered insecure?

Port 21 is used for FTP, which sends usernames, passwords, and data in plaintext without encryption.

What is the secure alternative to FTP on port 21?

SFTP on port 22 is the secure alternative, using SSH encryption to protect file transfers.

Why should Telnet on port 23 be avoided?

Telnet sends all communication in plaintext, making it highly vulnerable to man-in-the-middle attacks.

What is the secure replacement for Telnet?

SSH (Secure Shell) on port 22 replaces Telnet, encrypting remote terminal connections.

Is SMTP on port 25 secure?

No, SMTP on port 25 is insecure by default because it does not use encryption.

Which port is used for secure SMTP?

Port 587 uses SMTP with TLS encryption, securing email data in transit.

What is DNS over TLS?

DNS over TLS (DoT) encrypts DNS queries using TLS on port 853, preventing attackers from monitoring or tampering with DNS requests.

What is the difference between HTTP and HTTPS ports?

HTTP uses port 80 without encryption, while HTTPS uses port 443 with TLS encryption for secure web communication.

Why is NTP preferred over the old Time protocol?

NTP (Network Time Protocol) on port 123 replaces the older Time protocol, offering better error handling and more secure synchronization.

How do hackers exploit insecure ports?

Hackers can sniff unencrypted traffic, inject malicious data, or gain unauthorized access through poorly configured insecure ports.

What tools can scan for open ports?

Tools like Nmap, Masscan, and Zenmap are used to scan for open ports on a network.

Why is HTTPS important for websites?

HTTPS ensures data between a user’s browser and the server is encrypted, protecting login information and payment details.

Can DNS requests be encrypted?

Yes, using DNS over TLS (DoT) or DNS over HTTPS (DoH) encrypts DNS requests.

What are the most commonly exploited insecure ports?

Ports 21, 23, 25, 53, and 80 are among the most commonly exploited insecure ports.

How often should you audit your network ports?

Security experts recommend auditing open ports at least once a quarter, or after any major system update.

What is the role of a firewall in port security?

Firewalls block unwanted or insecure ports, helping reduce a network’s attack surface.

Are all open ports dangerous?

Not all open ports are dangerous, but they must be monitored and controlled to ensure only secure services are exposed.

How does a SIEM monitor port activity?

SIEM systems collect logs from firewalls, switches, and endpoints to detect abnormal port usage and potential threats.

What is port normalization in cybersecurity?

Port normalization ensures consistent port configurations across devices to avoid vulnerabilities due to inconsistent settings.

What happens if an insecure port is left open?

It can expose sensitive data and provide attackers an entry point into the network.

What is port hardening?

Port hardening involves closing unnecessary ports, using encryption, and configuring secure alternatives for essential services.

Should all port traffic be encrypted in 2025?

Yes, encrypting all port traffic is now considered a cybersecurity best practice in 2025.

How does port security impact compliance?

Using secure ports helps organizations comply with standards like GDPR, HIPAA, and ISO 27001 by protecting data in transit.

What is a real-world example of an insecure port breach?

In 2024, a university exposed student records via open FTP ports, emphasizing the risk of insecure services.

Can IoT devices have insecure ports?

Yes, many IoT devices ship with default settings that expose insecure ports, requiring manual security configuration.

What is the secure port for DNS?

Port 853 is used for DNS over TLS (DoT), providing encrypted DNS resolution.

Why is SFTP preferred over FTP in corporate environments?

SFTP encrypts both commands and data, preventing sensitive information from being exposed to attackers.

How do you close insecure ports?

Insecure ports can be closed using firewall rules, router configurations, and system security policies.

How do cybersecurity students learn about secure ports?

Through cybersecurity courses, labs, and hands-on network security training that cover port management and encryption protocols.