Common Server Exploits & How to Protect Against Them

If you're managing a server—whether it's through web hosting, running an app, or handling something behind the scenes—security should always be on your radar. Servers are a common target for cyberattacks, and it doesn't take much for a small weakness to turn into a major issue.

The good news? Most common exploits have well-known fixes. In this post, we'll break down some of the most frequent server attacks and walk through straightforward ways to protect your setup. Whether you're just getting started or looking to tighten things up, these tips can help you stay ahead.

1. SQL Injection (SQLi)

SQL Injection happens when an attacker inputs malicious code into form fields or URLs to manipulate your database. This can allow unauthorized access to data or even deletion of entire tables.

To prevent SQLi:

Use parameterized queries or prepared statements
These methods make it clear which parts of your code are instructions and which are user input, so attackers can't sneak in malicious commands. Most programming languages support this—like using ? placeholders in MySQLi or :value in PDO.

Validate and sanitize all user input
Never assume users (or bots) will input clean data. Always check that what's submitted matches what you expect—like only allowing numbers in an ID field, or stripping out unexpected characters from a text box.

Limit database user permissions
Don't give your web app more access than it needs. For example, if your app only reads data, don't give it permission to delete or edit anything. That way, even if an attacker gets in, they're limited in what damage they can do.

If you're running a CMS like WordPress, following best practices for WordPress security and hardening can help you guard against common SQL injection vulnerabilities.

2. Cross-Site Scripting (XSS)

XSS involves injecting malicious JavaScript into pages viewed by others. If executed, it can steal login cookies, log keystrokes, or redirect users to malicious sites.

To mitigate XSS:

Sanitize and validate input before displaying it
Make sure that any text users submit (like comments or search queries) is cleaned up before it's shown on your site. This means removing or converting special characters like < and > so they can't be treated as code.

Use output encoding
When displaying dynamic content, encode it so that browsers treat it as text, not as code. For example, &lt;script&gt; will show up as plain text instead of trying to run.

Apply a Content Security Policy (CSP)
A CSP is a set of rules you tell the browser to follow—for example, only loading scripts from trusted sources. Even if malicious code slips through, a strong CSP can prevent it from running.

If your server uses LiteSpeed, LiteSpeed Webserver features built-in security options that can help reduce the risk of XSS attacks while improving overall server performance.

3. Remote Code Execution (RCE)

RCE is a severe threat where attackers run their own commands on your server. If successful, they could control your system or deploy malware.

To reduce the risk of RCE:

Keep all software and plugins up to date
Security updates are released to fix known issues. Delaying these updates gives attackers a window to exploit vulnerabilities that already have public fixes.

Avoid using functions that execute system commands
If your code uses functions like exec() or system(), be extra cautious. Only use them if absolutely necessary and never with untrusted input.

Use a Web Application Firewall (WAF)
A WAF filters and monitors incoming traffic. It can detect suspicious patterns—like attempts to pass code through form fields—and block them before they hit your server.

For cPanel/WHM users, enabling protections like ModSecurity in WHM adds an extra layer of defense against remote code execution exploits.

4. Directory Traversal

Directory traversal allows attackers to access restricted files by manipulating file paths, often using patterns like ../ to move up directories.

To protect your server against Directory Traversal:

Sanitize file path input
Never allow user input to directly control file paths. Clean up anything users submit, and strip out characters like ../ that can be used to move around directories.

Use a whitelist of allowed files or directories
Instead of trying to block bad input, define a list of exactly what files or folders users are allowed to access. Anything else should be automatically rejected.

Set proper file permissions
Make sure sensitive files aren't readable by the public. For example, configuration files should not have read permissions for anyone except the server admin.

Misconfigured permissions can cause errors like 403s and leave you exposed. Here's a guide on fixing a 403 Forbidden error by properly configuring access control settings on your server.

5. Brute Force Attacks

Brute force attacks use automation to try various username/password combinations until one works. They often target SSH, FTP, or control panel logins.

How to guard against brute force attacks:

Use strong, unique passwords
Avoid using default credentials or simple passwords like "admin123." Use long passwords with a mix of letters, numbers, and symbols—and don't reuse them across services.

Limit login attempts
Set up your system to temporarily block IP addresses after several failed login attempts. This slows down automated scripts and makes brute force attacks less effective.

Enable two-factor authentication (2FA)
Even if someone gets your password, they won't get in without the second verification step—like a code from an app or text message.

Use SSH keys instead of passwords
For server access, switch from password-based login to SSH keys. They're much harder to crack and offer a safer way to authenticate.

A good starting point is changing your SSH port, which can make automated attacks less effective. Also, using SSH key-based authentication provides more robust protection than passwords alone.

6. Distributed Denial of Service (DDoS)

These attacks flood your server with traffic, causing it to slow down or crash. DDoS is especially dangerous as it comes from many sources and is nearly impossible to trace the source.

To reduce your exposure to DDoS attacks:

Use a Content Delivery Network (CDN)
Most people use Content Delivery Networks to deliver site content more effectively across multiple locations. The can also make it harder for attackers to overwhelm the origin server and filter out harmful traffic.

Set up rate limiting
Rate limiting restricts how often someone can make requests in a short time. If one user or IP is sending too many, they'll be temporarily blocked.

Monitor traffic for unusual spikes
Keep an eye on your traffic patterns. A sudden jump in visits—especially to a single endpoint—can be a sign of a DDoS attack.

Hide your origin server's IP
When attackers know your real server IP, they can target it directly. Using services that mask or proxy your IP can help absorb the blow.

You can protect your origin IP by using services like Cloudflare, which also brings other benefits of improved security and website performance.

For a deeper understanding of DDoS attacks, their risks, and mitigation strategies, refer to our article: What is a DDoS Attack? Risks, Prevention, Mitigation.

7. Outdated Software and Unpatched Vulnerabilities

Using outdated plugins, control panels, or CMS versions leaves you open to known exploits.

To reduce the risk of outdated software:

Set up a regular update schedule
Don't wait for things to break. Keep your OS, control panel, CMS, plugins, and server software on a regular update cycle—even if it means using automated tools.

Remove unused applications and services
Every extra tool or plugin is a potential risk. If you're not using it, uninstall it to reduce your attack surface.

Subscribe to update or security mailing lists
Software vendors usually announce security issues as they're discovered. Staying in the loop helps you patch before issues are exploited.

Use staging environments for testing updates
Test major updates on a clone of your live environment first, so you can spot problems without risking downtime.

Outdated scripts don't just create security risks—they can also slow down your website, affecting performance and reliability.

Regular maintenance increases server reliability, security, and overall  performance. Learn how to establish an effective maintenance routine in our guide: Creating a Server Maintenance Plan.

8. Misconfigured Permissions

Overly permissive file or directory settings are a quiet but serious vulnerability. They can allow attackers to access or modify sensitive data.

How to prevent this:

Apply the principle of least privilege
Give users and services only the access they need—no more. If someone only needs to view a file, don't grant write or execute access.

Regularly audit file and folder permissions
Periodically check which files are accessible and who can access them. Look for overly broad settings like 777 permissions that make files readable/writable by anyone.

Avoid using root access unless necessary
Running commands or services as root can be dangerous. If something goes wrong, it can affect your entire system. Stick to user-level privileges unless root is absolutely needed.

Use groups to manage access
Instead of setting permissions user-by-user, organize users into groups based on their roles. This keeps things cleaner and easier to manage securely.

Proper access control is key to avoiding errors like 403s. Revisit your settings using this guide on fixing 403 Forbidden errors to prevent unintended exposure.

Wrapping Up

Server security isn't just about firewalls and passwords—it's about building habits and systems that reduce risk over time.

Being aware of these common exploits and addressing them with practical solutions, you're not only protecting data—you're keeping services reliable and customers safe.

For a comprehensive overview of server hardening techniques, check out our article: What is Server Hardening & Why it Matters.