Security Vulnerabilities and Attacks: Server Threats and Solutions

Servers are constantly targeted by malicious attackers. Open ports, security vulnerabilities, and misconfigurations can all invite attacks. Remember, security is not a one-time setup — it's an ongoing process that requires monitoring and improvement.

Common Security Vulnerabilities and Attack Types

1. Brute Force Attacks

• Common in remote access services like SSH, FTP, and RDP.
• Attempts to crack passwords via trial-and-error methods.

2. DDoS (Distributed Denial of Service) Attacks

• Overwhelms server services with traffic to cause downtime.
• Often executed through botnets.

3. SQL Injection

• Malicious SQL queries injected into web forms to access the database.

4. Cross-Site Scripting (XSS)

• Malicious JavaScript is injected into a user’s browser to hijack sessions or deliver harmful content.

5. Zero-Day Vulnerabilities

• Exploits unknown or unpatched security flaws in systems.

6. Backdoors

• Malware or unpatched vulnerabilities that grant attackers long-term access.

7. Weak or Default Passwords

• Unchanged default passwords leave systems exposed.

Preventive Measures for Security Threats

1. Use Strong Authentication and Encryption

• Use key-based authentication instead of passwords for SSH access.
• Enable two-factor authentication (2FA) for added security.

2. Firewall and Access Controls

• Close unnecessary ports using ufw, iptables, or firewalld.
• Restrict SSH access to specific IPs:

sudo ufw allow from YOUR_IP to any port 22

• Use Fail2Ban to block repeated failed login attempts:

sudo apt install fail2ban
sudo systemctl enable fail2ban

3. Protect Against DDoS Attacks

• Use a CDN like Cloudflare to filter malicious traffic.
• Enable mod_evasive and mod_security on your web server.
• Monitor traffic with netstat -antp.

4. Apply Updates and Patch Management

• Regularly update your OS and services:

sudo apt update && sudo apt upgrade -y

• Apply security patches to defend against zero-day vulnerabilities.

5. Prevent SQL Injection and XSS

• Use prepared statements in SQL queries.
• Sanitize all user input in web forms.
• Apply Content Security Policy (CSP) headers to block malicious scripts.

6. Monitor Logs and Detect Suspicious Activity

• Review logs like /var/log/auth.log or /var/log/secure.
• Use ps aux --sort=-%cpu to check abnormal processes.
• Scan with chkrootkit or rkhunter to detect malware.

7. Use Automated Backup Solutions

• Back up important files and databases regularly.
• Ensure backups are stored securely.
• Consider using snapshots or RAID to prevent data loss.