A misconfigured security group previously resulted in a major security incident for a multinational e-commerce platform. The attackers were able to brute-force SSH logins for open SSH access and then brute-forced into the servers, unfortunately, breaching sensitive customer information.
Such an example illustrates quite well why you need to protect SSH access as much as possible to reduce the attack surface.
This blog tries to explore the risks of having uncontrolled Open SSH access, the advantages of tighter controls, and actionable steps to secure your network.
Understanding the Risks of Open SSH Access
SSH (Secure Shell) is a widely used protocol for secure, encrypted communication. However, when left open and unrestricted in security groups, SSH access becomes a prime target for cyber adversaries. Brute-force attacks, where attackers repeatedly attempt to guess login credentials, are a common method of exploitation.
The Mirai Botnet attack is a notable example of the consequences of unsecured ports. This malware leveraged open ports to compromise IoT devices globally, demonstrating the vulnerabilities associated with poor access control. Restricting Open SSH access is essential to prevent similar exploits.
The Benefits of Restricting Open SSH Access
Below we have listed the benefits of restricting open SSH acess:
- Reduced Attack Surface: Limiting access to specific IPs narrows the entry points for unauthorized users, making it significantly harder for attackers to infiltrate your network.
- Improved Visibility and Monitoring: Restricted access enables better monitoring and faster detection of anomalies, aiding in early threat identification.
- Regulatory Compliance: Enforcing stringent access controls helps meet compliance requirements such as GDPR, PCI DSS, and HIPAA, protecting your organization’s reputation.
How to Restrict Open SSH Access
To safeguard your network, implement the following measures:
- Use a Bastion Host
Bastion host acts as a secure gateway for SSH access, requiring users to authenticate through it before accessing other network systems.
IP Whitelisting
Limit SSH access to a select range of trusted IP addresses, effectively blocking connection attempts from unverified sources. Here’s how you can implement IP whitelisting using AWS CLI:
bash
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aws ec2 authorize-security-group-ingress –group-id sg-0123456789abcdef0 –protocol tcp –port 22 –cidr 203.0.113.0/24
- Implement Multi-Factor Authentication (MFA)
Add an extra layer of security by requiring MFA during login, ensuring protection even if credentials are compromised. - Regular Software Updates
Keep your SSH infrastructure updated with the latest patches to defend against newly discovered vulnerabilities.
Key Things to Consider When Securing Open SSH Access
- Audit Existing Security Groups: Regularly review security group configurations for open SSH access.
- Educate Your Team: Train administrators and users on best practices for secure access.
- Enable Logging: Use logging tools to monitor and analyze SSH access attempts, identifying and mitigating potential threats.
- Leverage Professional Services: Engage experts to conduct security assessments and penetration tests for comprehensive protection.
Conclusion
Securing Open SSH access is a critical aspect of minimizing your network’s exposure to potential threats. By employing strategies such as bastion hosts, IP whitelisting, and MFA, you significantly strengthen your defenses against unauthorized access.
Proactive measures and regular reassessments ensure your infrastructure stays resilient in an evolving threat landscape.
Partnering with cybersecurity experts, like those at SecureLayer7, can provide additional layers of assurance through advanced services such as Red Team assessments, Penetration Testing, and API Security Scanning.
Take action today to fortify your security groups and protect your digital assets against tomorrow’s threats.
