What Is a Vulnerability Scanner for Websites?
A website vulnerability scanner is a specialized tool designed to inspect and analyze a website for possible security gaps or weaknesses. These tools crawl through a site, much like a search engine robot, checking its structure, code, server settings, and more. The goal is to identify any potential vulnerabilities that could be exploited by hackers or malicious software.
These scanners can also play a crucial role in verifying the effectiveness of your security measures, ensuring that your defenses are up to par. They can identify gaps in protection, outdated software, and even the use of default or easily guessable passwords.
Vulnerability scanners must be used regularly to keep up with the ever-evolving landscape of web threats. New vulnerabilities are discovered every day, and hackers are always on the lookout for new ways to exploit them. Regular scanning ensures that you stay one step ahead of these cyber threats.
This is part of a series of articles about vulnerability assessment.
What Are the Common Web Vulnerabilities Detected by Vulnerability Scanners?
Vulnerability scanners can detect a wide range of vulnerabilities, from simple misconfigurations to complex code-based vulnerabilities. Let’s explore some of the most common types of vulnerabilities.
SQL Injection
SQL injection, often abbreviated as SQLi, is a type of vulnerability that occurs when an attacker can manipulate the SQL statements that a web application makes to its database. By inserting malicious SQL code into user inputs, an attacker could potentially access, modify, or even delete data from the database. This could lead to unauthorized access to sensitive information, data corruption, or even the complete takeover of the website.
Vulnerability scanners can detect potential SQL injection vulnerabilities by testing various inputs and observing the website's response. If the website behaves differently or returns an error message that reveals information about the database structure, the scanner would flag this as a possible SQL injection vulnerability.
Cross-Site Scripting (XSS)
Cross-site scripting, or XSS, is another common web vulnerability. This occurs when an attacker can inject malicious scripts into web pages viewed by other users. Such scripts can steal sensitive information like login credentials or personal details, manipulate website content, or even redirect users to malicious websites.
Vulnerability scanners can identify potential XSS vulnerabilities by attempting to inject a benign script into user inputs. If the script is executed when the page is viewed, the scanner will flag this as a possible XSS vulnerability.
Cross-Site Request Forgery (CSRF)
Cross-site request forgery, or CSRF, is a type of attack that tricks the victim into submitting a malicious request. This is done by forcing the user's browser to send a forged HTTP request, including the user's session cookie, to a website where they're authenticated. This could lead to unauthorized actions being performed on the victim's behalf.
Vulnerability scanners can detect CSRF vulnerabilities by looking for areas of the website that lack anti-CSRF tokens or other protective measures. If such areas are found, the scanner will flag them as potential CSRF vulnerabilities.
Security Misconfiguration
Security misconfiguration is a common vulnerability that occurs when a website or web application is incorrectly set up, leaving it exposed to potential attacks. This could involve anything from leaving default account settings unchanged to having unnecessary services running on the server.
Vulnerability scanners can identify security misconfigurations by comparing the website's current settings against a database of known secure configurations. If any discrepancies are found, the scanner will highlight these as potential security misconfigurations.
Insecure Direct Object References (IDOR)
Insecure direct object references (IDOR) are a common vulnerability where a web application exposes a reference to an internal implementation object. This can be as simple as a reference to a file or directory or as complex as a reference to a database record or key.
A vulnerability scanner can detect IDOR by testing various object references within your web application. If the scanner can manipulate these references to access unauthorized data, it indicates an IDOR vulnerability.
XML External Entities (XXE)
XML external entities (XXE) occur when an application processes XML data that includes a reference to an external entity. This can lead to disclosure of internal files, denial of service, or even remote code execution.
A vulnerability scanner can detect XXE vulnerabilities by sending various XML inputs to your application. If the application responds with data from an unexpected source, it indicates an XXE vulnerability.
Exposed PII
Personally identifiable information (PII) refers to any data that can identify an individual. This can include names, addresses, social security numbers, and more. If your website inadvertently exposes PII, it could lead to serious privacy breaches.
Vulnerability scanners can detect exposed PII by crawling your website and examining the data it sends and receives. If the scanner finds PII in places it shouldn't be, like URLs or error messages, it indicates a PII exposure vulnerability.
Remote Code Injection
Remote code injection is a serious vulnerability where an attacker can inject and execute their own code on your website. This could allow them to steal sensitive data, disrupt your service, or even take control of your site.
Vulnerability scanners can detect remote code injection by sending various inputs to your website. If these inputs cause unexpected behavior or output, it can indicate a remote code injection vulnerability.
Exposed Remote Desktop Service
Exposed remote desktop services, such as RDP (Remote Desktop Protocol) or VNC (Virtual Network Computing), can provide a direct entry point for attackers to your system. If these services are inadequately secured, they can become a significant vulnerability.
Vulnerability scanners can detect exposed remote desktop services by scanning your network for open ports associated with these services. If it finds any, it can test them for vulnerabilities like weak passwords or unpatched software.
How Does a Web Vulnerability Scanner Work?
A web vulnerability scanner operates by sending various inputs to your website and analyzing the responses. These inputs are designed to trigger potential vulnerabilities, and the responses can indicate whether a vulnerability is present.
The scanner begins with a process called 'crawling'. This involves navigating through your website, following links, and identifying all possible input points. This could include form fields, URL parameters, cookies, and more.
Once the scanner has identified these input points, it begins testing them for vulnerabilities. It does this by sending a range of specially crafted inputs, known as payloads, to each input point. These payloads are designed to trigger potential vulnerabilities.
The scanner then analyzes the responses to these payloads. If a response indicates a potential vulnerability, the scanner records it for further investigation.
Related content: Read our guide to vulnerability detection tools.
Tips from the Expert
Rob Gurzeev
CEO and Co-Founder
Rob Gurzeev, CEO and Co-Founder of CyCognito, has led the development of offensive security solutions for both the private sector and intelligence agencies.
In my experience, here are tips that can help you better utilize and enhance your use of website vulnerability scanners:
- Leverage differential scanning: Implement differential scanning to compare the current scan with the previous one. This can highlight new vulnerabilities introduced by recent code changes or configuration updates, helping to catch issues before they go live.
- Utilize custom payloads for complex applications: Modify the scanner’s payloads to suit the specific needs of your web application, especially if it's custom-built or uses unique frameworks. This ensures that the scanner tests the application effectively, avoiding false negatives.
- Correlate with threat intelligence feeds: Use threat intelligence feeds to update your scanner with the latest vulnerability signatures and emerging threats. This ensures that your scans are always relevant to the current threat landscape.
- Monitor scanner performance: Track the performance of your vulnerability scanner over time, including the rate of false positives and scan duration. Optimize settings and payloads to improve accuracy and efficiency, reducing the time between scans and the need for manual verification.
- Use multi-scanner approaches: Different scanners often excel at detecting different types of vulnerabilities. Combine the use of multiple vulnerability scanners to improve overall coverage and reduce the chances of missing critical security issues.