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Is Port 22 Secure? A Practical Guide to SSH Security

Is Port 22 Secure? A Practical Guide to SSH Security

Port 22 is the default channel for the Secure Shell (SSH) protocol, the primary method administrators use to manage remote Linux and Unix systems. As a security practitioner, you’ll often hear the question: is port 22 secure? The short answer is not inherently. The port number alone does not determine security. What matters is how SSH is configured, monitored, and integrated into a layered defense. This article explains why port 22 is a known target, what truly strengthens SSH security, and practical steps you can take to harden it without sacrificing productivity.

Understanding the role of port 22 in SSH security

When a device on the internet listens on port 22, it signals that SSH connections can be established to that host. Attackers routinely scan for such hosts, attempt credential stuffing against SSH, and probe for misconfigurations. In other words, an open port 22 is a potential doorway, not a guarantee of compromise. The real question is how effectively you reduce risk once an attacker gains access to your server. This means focusing on authentication methods, access controls, monitoring, and ongoing maintenance rather than relying on the port being 22 alone.

Key concepts that influence SSH security

Several principles guide a robust SSH setup:

  • authenticated access should be strong and unique to each user;
  • access should be limited to legitimate users and trusted networks;
  • encryption must protect against eavesdropping and tampering;
  • the server should be regularly updated to protect against known vulnerabilities;
  • continuous monitoring and rapid incident response are essential to detect and respond to abuse.

With these principles in mind, you can turn port 22 from a potential liability into a controlled access point that supports operational needs without exposing sensitive systems to unnecessary risk.

Practical hardening techniques for SSH

The following measures form a practical, defense-in-depth approach to SSH security. They are common-sense steps that work across many environments to reduce the attack surface while keeping legitimate users productive.

Use key-based authentication and disable password login

One of the most effective protections is to use SSH key pairs for authentication instead of passwords. With key-based authentication, an attacker cannot simply guess a password; they would need possession of a private key. Ensure the private key is protected with a strong passphrase and that public keys are managed securely on the server.

  • PubkeyAuthentication yes
  • PasswordAuthentication no
  • ChallengeResponseAuthentication no

To enable key-based access, generate a key pair with a current cryptographic standard (for example, RSA with a sufficient key length or an Ed25519 key) and place the public key in the appropriate authorized_keys file for each user. Consider adding passphrase protection and using an SSH agent with a hardware-backed key where feasible.

Disable root login and limit user access

A common misstep is allowing direct root login via SSH. If an attacker compromises the account with sudo privileges, they can escalate privileges quickly. Disable direct root access and enforce least privilege for SSH sessions.

  • PermitRootLogin no
  • Use a normal user account for SSH and escalate with sudo when needed
  • AllowUsers or AllowGroups to restrict which accounts can authenticate

Restricting access to a known set of users reduces the number of possible vectors an attacker can explore. It also simplifies auditing and incident response.

Limit session and authentication attempts

Controlling how long a connection can attempt to authenticate and how many tries are allowed helps mitigate brute-force attacks.

  • MaxAuthTries 3
  • LoginGraceTime 30s
  • UseDNS no

These settings reduce the window of opportunity for automated attacks and improve authentication reliability.

Employ strong cryptography and protocol controls

Always use SSH protocol 2 and avoid deprecated algorithms. Disable outdated ciphers and MACs when possible, and ensure you are using modern key exchange methods.

  • Protocol 2
  • Pubkey, Ed25519 keys are preferred for strength and performance
  • Disable weak ciphers and obsolete algorithms

Keeping the cryptographic defaults contemporary lowers risk from cryptographic weaknesses and compatibility issues.

Consider network controls and access bridges

Beyond server-side hardening, network-layer controls can dramatically reduce exposure.

  • Use a firewall to limit SSH access to known, trusted IP addresses or ranges
  • Implement a jump host (bastion) or VPN to restrict direct SSH exposure to the public internet
  • Implement port knocking or bring-your-own-vpn strategies if appropriate for your environment

While changing the default port away from 22 can reduce noise, it should not be relied on as a sole security measure. A consistent, well-monitored configuration with strong authentication remains essential.

Enable additional authentication factors where possible

Two-factor authentication (2FA) for SSH adds a critical layer of defense. Solutions like Duo, Google Authenticator, or other 2FA providers can be integrated with PAM or SSH configurations to require a second factor in addition to the key or password.

  • Integrate 2FA for SSH login
  • Prefer hardware keys where feasible for higher assurance

Log, monitor, and respond

Security is not set-and-forgot. Implement robust logging and monitoring so you can detect anomalies fast and respond effectively.

  • LogLevel VERBOSE or INFO
  • Syslog facilities for auth logging
  • Regular review of authentication failures and access patterns
  • Automated alerts for unusual login activity

Regularly reviewing SSH logs helps you identify misconfigurations, unauthorized access attempts, and potential credential compromises before they escalate.

Keep SSH software up to date

Ongoing maintenance matters as new vulnerabilities are discovered and patched. Ensure your SSH server (and the underlying OS) receives timely security updates and that configurations are kept in a documented, auditable state.

What to consider beyond local hardening

Port 22 is just one piece of a broader security strategy. For many organizations, the risk is reduced further by combining SSH hardening with network segmentation, centralized authentication, and policy-driven access control.

  • Use an identity provider for centralized access management
  • Adopt a jump host or VPN to minimize exposure of SSH services on the public internet
  • Regularly review SSH keys and revoke unused keys promptly
  • Document SSH access policies and ensure auditors can verify compliance

In practice, combining strong authentication (key-based, with optional 2FA), strict access control, and vigilant monitoring creates a more resilient posture than any single tactic could provide. Port 22 remains the most common surface for SSH, but with careful configuration and ongoing discipline, it does not have to be a software liability.

Common mistakes to avoid

Even experienced administrators occasionally fall into traps that undermine SSH security. Be mindful of these pitfalls:

  • Leaving PasswordAuthentication enabled on important hosts
  • Using the root account for day-to-day SSH access
  • Neglecting to restrict access to only necessary users or networks
  • Relying solely on changing the port from 22 as a security measure
  • Failing to rotate or revoke SSH keys when personnel changes occur

Testing and validation: how to verify your SSH security

Periodically validate your SSH configuration to ensure it aligns with best practices and meets compliance requirements. Useful checks include:

  • Review the sshd_config file for the settings described above
  • Test authentication with a non-privileged user before applying changes to production
  • Run vulnerability scans or SSH audit tools that assess protocol versions, ciphers, and key lengths
  • Perform a controlled penetration test to simulate real-world attack scenarios

These tests help confirm that port 22 is secure in practice, not just in theory, and that defense-in-depth measures are functioning as intended.

Conclusion

Is port 22 secure? The answer is nuanced. Port 22 by itself is not a guarantee of security, but it can be part of a secure, well-maintained SSH strategy. By adopting key-based authentication, disabling password logins, restricting access, enabling two-factor authentication, applying strict session controls, employing network barriers such as VPNs or jump hosts, and maintaining vigilant monitoring and timely updates, you significantly reduce the risk of unauthorized access. In the end, a secure SSH deployment is less about the port number and more about disciplined configuration, continuous improvement, and proactive defense against evolving threats.