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A customer’s internet-facing system was compromised after attackers brute-forced an exposed SSH port (logged as sshd: Accepted password for postgres from 89.163.X.X port 22010 ssh2). This highlights critical gaps in perimeter security, including unmonitored open ports and weak passwords.
You Should Know:
1. Secure SSH Access
- Disable Password Authentication: Use SSH keys instead.
sudo sed -i 's/#PasswordAuthentication yes/PasswordAuthentication no/g' /etc/ssh/sshd_config sudo systemctl restart sshd
- Change Default Port: Reduce automated scan risks.
sudo sed -i 's/#Port 22/Port 2222/g' /etc/ssh/sshd_config sudo systemctl restart sshd
2. Monitor Open Ports
- Check Exposed Services:
sudo netstat -tulnp | grep LISTEN sudo ss -tulnp
- Shodan Monitoring: Use tools like Shodan to detect unintended exposures.
3. Block Brute-Force Attempts
- Fail2Ban: Automatically ban malicious IPs.
sudo apt install fail2ban sudo systemctl enable --now fail2ban
- Manual IP Blocking:
sudo iptables -A INPUT -s 89.163.X.X -j DROP
4. Enforce MFA for SSH
- Google Authenticator Setup:
sudo apt install libpam-google-authenticator google-authenticator
Edit `/etc/pam.d/sshd` and add:
auth required pam_google_authenticator.so
5. Log Auditing
- Review SSH Logs:
sudo grep "Failed password" /var/log/auth.log sudo journalctl -u sshd --since "1 hour ago"
What Undercode Say
Perimeter security requires proactive measures:
- Regular port scans (
nmap -p- <IP>). - Patch management (
sudo apt update && sudo apt upgrade). - Network segmentation (
iptables/nftablesrules). - Strong passwords (
pwgen 16 1). - Automated alerts (
logwatch/Splunk).
Expected Output:
A hardened SSH setup with reduced attack surface, logged intrusion attempts, and active monitoring.
Relevant URLs:
References:
Reported By: Stephan Berger – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
