Open Ports and Outdated Protocols: A Hacker’s Paradise Lost
Cybersecurity Assessments | Audit Readiness
Published: Apr 17, 2025
In cybersecurity, identifying and assessing vulnerable services is essential for effectively protecting an organization’s security stance. Two crucial elements that influence service security are protocols and ports.
Weak cybersecurity practices such as open ports and outdated protocols cause significant vulnerabilities that can put your organization at risk for damaging data breaches and security attacks. Cybercriminals constantly scan for open ports, which can reveal insecure services, misconfigurations, and other weaknesses they can exploit. Fortunately, however, there are measures you can take to ensure you minimize that risk and adequately secure your network.
In this blog, we will explore how protocol versions and ports correlate with one another and how they can impact security, as well as provide guidance on how to identify potentially vulnerable services.
What Is a Protocol and Why Is It Important?
A protocol is a set of rules for formatting and processing data between different devices in the same network. Protocols allow connected devices to communicate with each other. Think of this as the language that two different systems or services use to talk to each other, ensuring they understand and process information correctly. These protocols are important because they strengthen your overall security posture and help prevent cyber-attacks by ensuring confidentiality, integrity, and authentication. However, outdated versions of protocols may include known vulnerabilities that attackers can exploit.
What Is a Port and Why Is It Important?
A port is a virtual communication endpoint used by computers to send and receive over a network. Ports are crucial for managing network functionality as they enable different services to operate simultaneously on a single device. Ports are assigned to specific services and applications to ensure that data is directed to the correct destination, preventing conflicts and organizing network traffic efficiently. Some ports are notable targets for attacks, while others may show indications of insecure or misconfigured services. Therefore, it’s important to monitor and restrict port activity to reduce the risk of vulnerabilities.
The Risks of Outdated Protocol Versions
Many protocols evolve over time to address security flaws. Using outdated versions can leave an organization prone to exploitation.
Below are examples of common protocols and the risks with their older versions:
SSH (Secure Shell)
- Risk: Older SSH versions are vulnerable to man-in-middle attacks, weak encryption, and credential sniffing.
- Best Practice: Ensure that only SSH-2 is enabled, utilizing strong cryptographic algorithms and disabling weak ciphers.
SNMP (Simple Network Management Protocol)
- Risk: SNMPv1 and SNMPv2c transmit data in plain text, making them prime targets for interception and spoofing.
- Best Practice: Use SNMPv3, which supports encryption and authentication, which helps prevent unauthorized access.
TLS (Transport Layer Security) & SSL (Secure Sockets Layer)
- Risk: SSLv2 and SSLv3, and TLS 1.0 & 1.1 are vulnerable to exploits to attacks like POODLE and BEAST, which allows attackers to decrypt sensitive traffic.
- Best Practice: Enforce TLS 1.2 or TLS 1.3 and disable weak cipher suites in web and email servers.
For more information on TLS and strong ciphers, read our blog How use strong protocols and cipher suites.
RDP (Remote Desktop Protocol)
Remote Desktop Protocol (RDP) is the ability to connect remotely to a non-physical computer from a local computer.
- Risk: Older versions of RDP (before Windows Server 2016) have known vulnerabilities like BlueKeep, which allowed attackers to execute any code they want a computer. BlueKeep was a worm that spread to all computers within a network without any actions from users.
- Best Practice: Use Network Level Authentication (NLA), a security feature that requires users to authenticate before establishing a session with a remote system.
SMB (Server Message Block)
Secure Message Block (SMB) is a communication protocol that allows users to communicate with remote servers and computers, which they can open, share, edit files, and even share and utilize resources.
- Risk: SMBv1 is a common attack vector for ransomware and exploits.
- Best Practice: Disable SMBv1 and enforce SMBv3 with encryption.
The Risks of Open Ports
While outdated protocols introduce vulnerabilities, open ports determine how attackers can reach them. When a service is running on its default port and is not safeguarded, it can become a target.
Common Ports considered High-Risk:
|
Port |
Service |
Security Risk |
Mitigation |
|---|---|---|---|
|
20/21 |
FTP |
No encryption, credentials in plaintext |
Use SFTP (SSH FTP) or FTPS (FTP over TLS) |
|
23 |
Telnet |
Unencrypted login, susceptible to eavesdropping |
Replace with SSH |
|
25 |
SMTP |
Can be used as an open relay for spam |
Require TLS encryption and authentication |
|
53 |
DNS |
Vulnerable to DNS spoofing and DDoS attacks |
Use DNSSEC, restrict recursion |
|
80 |
HTTP |
No encryption, traffic vulnerable to interception |
Use HTTPS with TLS 1.2 or higher |
|
110 |
POP3 |
Plaintext authentication, easy authentication theft |
Use POP3S (SSL/TLS) |
|
139/445 |
SMB |
Vulnerable to malware like WannaCry |
Disable SMBv1, restrict external access |
|
3389 |
RDP |
Targeted for brute-force & exploits |
Restrict access and enforce NL |
|
445 |
SMB |
Exploited for lateral movement in networks |
Restrict to internal use, enforce SMBv3 |
|
161/162 |
SNMP |
Can leak network details if misconfigured |
Enforce SNMPv3, disable public community strings |
|
22 |
SSH |
Brute force attacks, credential theft |
Use strong authentication, change default port |
|
5060 |
SIP (VoIP) |
Susceptible to eavesdropping and spoofing |
Encrypt SIP traffic, use TLS |
|
1433 |
MSSQL |
Often targeted for database breaches |
Restrict access, enforce authentication |
|
1521 |
Oracle DB |
Database exploitation and unauthorized access |
Use firewall rules, enable encryption |
|
3306 |
MySQL |
SQL Injection, unauthorized access |
Restrict remote connections, enforce authentication |
|
5900 |
VNC |
Remote desktop hijacking |
Use VPN, strong passwords and encryption |
Best Practices for Securing your Network
To effectively protect your network from cyber threats associated with open ports and outdated protocols, implementing strong security measures is essential. By following best practices for network security, your organization can reduce vulnerabilities, detect potential risks, and strengthen your overall security posture. A layered approach that combines proactive monitoring, access controls, and regular audits can help safeguard critical assets from malicious attacks.
Here are some key best practices to secure your network:
1. Harden Services
- Upgrade to secure protocol versions and disable outdated ones
- Eliminate unnecessary services and ports, restrict access using firewalls
2. Enforce Strong Authentication
- Implement multi-factor authentication (MFA) and require strong passwords.
- Use tools like vulnerability scanners and network traffic monitors like Wireshark to detect risks
3. Regular Audit Configurations
- Disable weak ciphers and enforce modern standards like SNMPv3
- Continuously review port and service configurations to align with security policies
Reducing Security Risks Through Protocol and Port Management
Ensuring secure and updated protocol versions and properly managing open ports are necessary for successfully reducing security risks. Regular audits, proper configurations, and vulnerability scans can help organizations detect and mitigate threats before they become exploits.
If you have further questions about cybersecurity best practices, Schellman is here to help. Contact us today and we’ll get back to you shortly. In the meantime, discover other helpful cybersecurity insights in these additional resources:
About Natasha Camacho
Natasha Camacho is a senior associate at Schellman based in Lutz, Florida, who works in the SOC service line. Prior to joining Schellman in 2022, Natasha worked in Product Management at J.P. Morgan, working in payments and sanctions. Natasha is now focused primarily on SOC reporting for organizations across various industries.