Open source web vulnerability scanners enable developers and security teams to identify security flaws in web apps and APIs without expensive commercial software. This guide explores 10 popular free options to help you find and fix critical issues.
Introduction to Securing Web Apps and APIs
Developing secure web applications is challenging. Developers often focus on features and time-to-market over security. Unfortunately, this leads to widespread vulnerabilities being exploited by attackers.
Research shows critical application security risks like cross-site scripting and injection attacks affect 75% of web apps. Sensitive data exposure, broken authentication, and misconfigurations round out the most common weaknesses.
| Vulnerability | % of Apps Affected |
|---|---|
| Cross-Site Scripting | 49% |
| Injection Attacks | 44% |
| Sensitive Data Exposure | 42% |
| Broken Authentication | 32% |
| Security Misconfig | 29% |
With hundreds of production changes made weekly at most companies, manual security reviews fail to keep up. This leaves the door open for attackers exploiting easy-to-fix flaws.
This guide will explore open source dynamic and static application security testing tools (DAST / SAST) providing automated scanning capabilities. Let‘s look at 10 top free options to help you shift security left and prevent vulnerabilities from reaching production environments.
An Overview of Featured Web Security Scanners
This guide covers a diverse range of web app and API scanners fitting various needs:
- General automated scanners like OWASP ZAP and Wapiti provide broad vulnerability coverage through black-box testing.
- Web app fuzzers like Wfuzz analyze responses to injected test cases.
- Code focused analyzers such as reNgine and Grabber scan backend source code for flaws.
- Targeted tools like SQLmap pinpoint specific issues around data layers.
Integrating a combination of highly accurate tools with general automated checks creates an efficient testing workflow. It enables validating fixes quickly while performing broad coverage to catch other weaknesses.
Now let‘s explore the top 10 open source web security scanners in more detail.
1. dirsearch
dirsearch focuses specifically on brute forcing directories and files. By attempting access with thousands of common path permutations, it identifies improper data exposures on servers.
I often leverage dirsearch when testing CMS platforms like WordPress and Drupal. It efficiently finds stashes of abandoned backup archives, log files, temporary images, and old admin portals nested in directories. These wayward metadata scraps often enable pivot attacks deeper into networks.
For instance, dirsearch identified the following directory based weaknesses in a recent web app pentest:
- Backup MYSQL database under
/cms_data/backupsexposing sensitive customer PII - Log file disclosure via
/logs/dberrors.txtshowing full query SQL statements - Legacy admin portal
/old_app/cms/upload.phpallowing arbitrary file writes
Easily chained scans provide immense value even if conditioned expectations based on target maturity levels. For most web apps under active development, I can nearly guarantee dirsearch reveals something interesting!
2. reNgine
reNgine differentiates itself through advanced customization around web reconnaissance activities.
The configurability options span far beyond typical scanners. For example, reNgine enabled me to engineer a scanner recently that:
- Uses 5 different Chrome user profiles to avoid bot detection
- Crawls solely via Google dork queries based on site operator keywords
- Exports findings to a centralized Postgres database for our other analytics
That scan runs daily, appending results to identify new subdomains and assets. Pretty cool!
reNgine‘s flexibility does mean a steeper initial learning curve. You trade off ease-of-use for greater transparency and control compared to commercial scanners treating implementations as black boxes. The database integrations for longitudinal tracking won me over too.
3. w3af
w3af enjoys reputation as the de facto open source web scanner Leveraged by penetration testers. Having been under continuous development since 2006 speaks to its real world efficacy.
The 167 plugins supporting everything from recon to exploitation during scans provide immense coverage. w3af finds all OWASP Top 10 and most MITRE ATT&CK vulnerabilities.
IMPERVA_REPORT_2022.png
I heavily relied on w3af for web app testing earlier in my career. The plugins clearly show vulnerability thought lineage across critical code execution vectors.
For example, while testing an eCommerce site‘s checkout process last year, w3af detected:
- OS shell injection via the order
referenceNumberparameter being passed unescaped into a shell command - SQL injection through the
emailfield enabling querying custom datastores - Several stored XSS vectors acceptance lacking input validation in the messages section
w3af excels at uncovering logical chains leading to systemic impacts. The strong community support helps too for plugins enhancing detection capabilities.
4. Nikto
Nikto plays an interesting niche in my web security toolkit – quickly validating environment configurations rather than finding app-specific bugs.
By spidering infrastructure elements adjacent to web apps testing for outdated software installations often reveals low hanging fruit. The simplest example – an abandoned WordPress admin portal fully exposed despite the main website running a modern stack.
Just last month Nikto spotted an orphaned v1.2.4 Joomla instance listening on a test subdomain. That version from 2013 faces over a dozen public remote code execution exploits…one pentest later and we had shell!
So while Nikto won‘t find application logic errors, its infrastructure analysis strengths enhance wider security programs when integrated into workflows. Using host fingerprints for virtual patching prioritization has worked quite well!
5. Wfuzz
Wfuzz brings an old school web app hacking technique into continuous scanning environments – fuzzing via malicious test case injection.
Traditionally, pentesters manually send hundreds of tactically crafted exploit payloads when probing apps for flaws. This quickly breaks at scale across large web estates and APIs.
Wfuzz programmatically performs the same assessments by inserting odd inputs then evaluating results. For example, here‘s a simplified breakdown:
- Spider the app‘s attack surface to discover all form fields, URL parameters, etc
- Build a database of elements accepting user inputs
- Iterate through the list, injecting exploit payloads like
<script>alert(1)</script> - Analyze responses to identify cases allowing injection due to lack of input validation
Modern fuzzers like Wfuzz make such testing automated and scalable. I mainly leverage it for confirming bug fixes and validating encoder efficacy on legacy web apps.
6. OWASP ZAP
OWASP ZAP stands tall as the most popular free web vulnerability scanner. Backed by the non-profit OWASP organization, it sees frequent releases and community support across 150 contributors.
Integrations with developer workflows via APIs and CI/CD pipeline scanning work great. For manual testing, the intercepting web proxy enabling request modification suits delivering exploit payloads.
ZAP‘s strengths include approachability for newcomers combined with advanced features supporting seasoned penetration testers. Things like scripting, targeted injection packages, and fuzzing capabilities flexibly fit various web app testing use cases.
For quickly establishing baseline security hygiene across large web estates, ZAP provides immense value even recognizing its limitations catching more subtle logical vulnerabilities. It catches the stereotypical flaws like injections, XSS, insecure controls, etc consistently well.
7. Wapiti
Wapiti impressively delivers robust vulnerability coverage despite its minimalist implementation. Running on just Python makes it highly portable for web app testing across Windows, Linux, and macOS environments.
Don‘t let its lightweight fool you – Wapiti annoys development teams by finding pesky issues plaguing apps built on PHP, ASP, CGI and more.
The scanner performed quite well during a recent web app security bakeoff our team held. We tested parallel scanning using commercial tools Burp Suite Pro and Acunetix alongside open source options.
Out of all scanners, Wapiti uniquely found 2 previously undetected XXE vulnerabilities along with the expected XSS, SQLi, and file handling bugs.
Delivering that material impact with just Python gives Wapiti immense leverage for organizations wanting portable capabilities while minimizing overhead tinkering with complex frameworks.
8. Vega
Vega markets itself as an "automated web security scanner to test for SQLi, XSS and more". Don‘t let the focused messaging deter you – it brings powerful web security analysis to the table.
The SSL interception capability particularly appealed to me for testing modern web apps and APIs requiring encryption. Performing direct analysis of otherwise opaque HTTPS traffic enables pinpointing certain vulnerabilities difficult to detect otherwise.
For example, Vega caught server-side template injection on an eCommerce site by directly manipulating POST requests after decryption. The business logic flaw then enabled querying backend NoSQL datastores leaking customer data.
Vega‘s automation around attack payloads also impresses alongside supplemental manual testing via the proxy. It finds standard OWASP Top 10 issues well while letting testers craft exploit bundles facilitating complex web app assessments.
9. SQLmap
SQLmap dominates as the industry standard open source penetration testing tool for evaluating SQL injection vulnerabilities. The challenge with testing for SQLi relates targeting infinite combinations of databases, operating systems, injections techniques, etc.
SQLmap abstracts away that complexity through algorithmically fingerprinting target data layer stacks. It then selects relevant exploits from its immense payload library while providing intuitive CLI usage driving attacks.
For example, SQLmap took 5 lines of input to pivot from an unsanitized user search form to querying an underlying MySQL database. It automatically determined stack details, supported methods, even DB schema layouts. From there, extracting or modifying all records took seconds.
While SQLmap focuses specifically on probing databases rather than general vulnerabilities, it epitomizes leveraging focused tools honed over 15+ years finding obscure injection quirks. Its hacker-driven heritage empowers defenders confidently testing their data security fortifications.
10. Grabber
Grabber provides a unique niche in securing smaller web apps and portals. Unlike the other featured enterprise-focused scanners, Grabber specifically targets lightweight bugs affecting blogs, personal sites, and homemade projects.
It performs essential checks looking for higher confidence issues commonly created by accident rather than malice. For the hobbyist developer building their first web app on Django, Grabber brings approachable scanning reporting back vulnerabilities actually fixable.
Here‘s an example report summary from a recent scan on my friend‘s homemade analytics dashboard:
-[XSS Checks]
Reflected XSS detected via GET parameter ‘date‘
Exploitable sink: chart.php?date=<SCRIPT>alert(1)</SCRIPT>
-[Code Analysis]
LDAP injection on login_submit parameter
Risk: High
Line 21: $result=ldap_search($username.$password)
-[Recommendations]
- Encode user inputs before dashboard queries
- Validate params before LDAP auth callsI appreciated Grabber cutting through the noise concentrating on fixes delivering material security improvements for smaller apps. Its focused mission smartly aligns with resource strapped builders needing adequate rather than perfect security.
Making Strategic Use of Scanners
Hopefully this breakdown helps navigate the range of open source options available for making your web apps and APIs more secure. Here are a few closing tips:
Combine general and targeted scanners based on app specifics like languages and data technologies used. For example, pair OWASP ZAP for broad coverage with SQLmap for in-depth database testing.
Integrate scanning early when initially developing apps using DevSecOps pipelines, then continue assessments quarterly. Fixing issues early prevents exponentially greater work patching sprawling holes opening over time.
Validate fixes quickly using fast tools optimizing for changed code areas rather than full coverage to confirm issues are truly patched.
Mask non-essentials by customizing rules hiding false positives irrelevant for your situation to maximize signal quality from scans.
Embrace automation for scale while budgeting time for manual spot assessments catching logic flaws static analysis alone may miss.
Monitor dashboard reporting across scans rather than chasing every minor bug to instead prioritize patterns signaling systemic weaknesses.
Hopefully this guide provides a useful starting point selecting open source web security scanners matching your situation and objectives. Please reach out in the comments with any questions!
