SAST vs DAST, SCA and IAST: which scan proves what, and which ones a small team needs

For a small team, SAST vs DAST has a plain answer: both, in order. Put dependency scanning and a free SAST scan on every pull request first, then add a passive DAST baseline scan against staging before each release, and leave IAST for later. SAST and DAST read different things: your source code, and the running app.

What we are comparing, and for whom: SAST, DAST, SCA and IAST as security testing tools

Application security testing comes in four scan types. SAST reads your source code. DAST sends requests to the running app. SCA reads the dependency list against vulnerability databases. IAST watches from an agent inside the app while tests run. Each answers a different question, and none of them knows what your app is supposed to allow.

All four sit inside the wider job of web app security, and each covers one slice of it. The reader I have in mind is a team of one to five people with a CI pipeline, or about to set one up; if that pipeline doesn’t exist yet, start with CI/CD best practices and come back.

Here are the four in the words of OWASP’s Developer Guide and NIST. Static application security testing “analyzes the code without running it”. Dynamic application security testing “applies input to the application while running it in a sandbox or other isolated environments”, and OWASP’s DAST page calls it a black-box test that talks to the app “through the web front-end”. Software composition analysis is used “to identify open-source and third-party components in use in an application, their known security vulnerabilities, and typically adversarial license restrictions”. Interactive application security testing tools are “typically implemented as an agent within the test runtime environment”. OWASP’s DevSecOps Guideline lists all four among the steps it would put in a basic pipeline.

Searches for security test tools or cybersecurity testing tools often return ranked lists. The table below is my answer instead: a scan type per question, because the right tool follows from what you need to know. End-to-end application security testing is, in my reading, the vendor phrase for buying all four from one platform. So SAST vs DAST vs IAST, or SAST vs DAST vs SCA, has no single winner: SCA, SAST, DAST and IAST each read something the others can’t. This page is documented analysis from OWASP, NIST and each tool’s own docs, not a benchmark.

The first four columns follow OWASP and NIST; the last column, what each scan tends to turn up, is my reading.

SAST vs DAST: which scan proves what

SAST vs DAST is inside against outside. SAST reads your code, including paths no request reaches, and is frequently unable to find configuration issues. DAST sees only what it can reach in the running app, and what it reports is real behavior. SAST and DAST scans answer different questions, so a small team runs both.

The difference between SAST and DAST shows up in what each can say. SAST points at the file and line, and OWASP lists “High numbers of false positives” among its weaknesses, along with being “Frequently unable to find configuration issues, since they are not represented in the code”. DAST tools “do not have access to the source code”, so a DAST finding can’t name the line at fault, but it comes from the app’s actual response. The noise on one side and the real behavior on the other are my reading of those two definitions, which is why a DAST vs SAST scan comparison ends with both rather than one.

What a customer’s security form really asks is whether you can back a sentence. The table below is my reading of which scan can support which sentence, and where SAST and DAST scanning both run out.

The last two rows are where SAST and DAST testing both stop. ZAP’s own docs say “Logical vulnerabilities, such as broken access control, will not be found by any active or automated vulnerability scanning.”

Row five is not a corner case. 7 of the 21 third-party apps had confirmed cross-user or cross-tenant authorization failures, where a logged-in user could read or write another customer’s data. Those 21 are apps I audited in June and July 2026, a selected set of audited apps, not a random sample and not a rate for AI-built apps in general.

For the structural blind spots, category by category, see what each scanner category cannot see. If the question behind “what is SAST and DAST” is really what a code scan does and which one fits your language, that is covered in what a code scan is. Choosing a SAST product and reading its report belong to static code analysis tools.

What DAST testing is: a DAST scan probes the running app from outside

DAST testing probes a running app from outside, the black-box way. A passive scan watches the traffic of a crawl and reports what it sees, such as missing headers and cookie flags. An active scan sends attacks, and ZAP’s own docs warn that actual damage can be done to a site’s functionality and data. Passive first; active on staging.

In cyber security terms, DAST (dynamic application security testing) is the black-box method: DAST scanners talk to a web application “through the web front-end” and “detect vulnerabilities by actually performing attacks”. That is also why DAST in cybersecurity writing gets called a black box scan: the scanner crawls the app, sends requests and reads the responses, with no view of the code. A DAST scan run by ZAP comes in two modes, and the difference matters more than any tool choice.

The baseline scan spiders the target, then waits for passive scanning, so it “doesn’t perform any actual ‘attacks’”, and ZAP says the script “is intended to be ideal to run in a CI/CD environment, even against production sites”. Active scanning is the other mode. ZAP’s page on active scanning says “Active scanning is an attack on those targets” and “You should NOT use it on web applications that you do not own.” Its getting-started page adds that “actual damage can be done to a site’s functionality, data, etc.”

Picture a founder who copies a CI template that runs ZAP’s full scan and points it at the live production URL, so the report covers the real thing. The full scan runs a full active scan, which ZAP says “does perform actual ‘attacks’”, so every form the spider found is now a target in production, where ZAP’s warning about damage to a site’s data applies to real customers. The baseline scan is the one ZAP intends for CI, even against production sites; the full scan belongs on staging, with data nobody needs.

DAST scanning, in my reading, is good at the things a response gives away: security headers, TLS and cookie settings, exposed files, reflected injection, and error pages that leak stack traces. Which headers to set, and how, is a topic of its own. What a DAST scan needs to be useful is a login it can hold, which is the hard part, and it is covered in authenticated scanning that proves it stayed logged in.

Dynamic scanning of a single-page app needs a crawler that runs the JavaScript, since dynamic scans with a plain spider see little of it. ZAP’s baseline scan has the -j option for this, which its docs describe as “use the modern spider in addition to the traditional one (default: Ajax spider)”. A DAST automated test, in my working rule, is the same scan run by the pipeline before each release or on a schedule, not a one-off.

Open source DAST: what a ZAP baseline scan does, and DAST images for CI

Open source DAST usually starts with ZAP, which ships official Docker images and packaged scans. Its baseline scan crawls for one minute by default and runs passive checks only, so it fits a CI job. The full scan adds an active scan and belongs on staging. Nuclei adds template-driven checks when you want a specific known test.

Of the open-source DAST tools, ZAP is where I’d start. ZAP’s baseline scan runs the spider “for (by default) 1 minute and then waits for the passive scanning to complete before reporting the results”, while the full scan adds “a full active scan”. ZAP’s docs now carry the line “ZAP by Checkmarx”, and the project stays open source.

DAST images, in the CI sense, are the scanner’s container images. ZAP publishes official ones, ghcr.io/zaproxy/zaproxy:stable among them, and every image except bare carries the packaged scan scripts, so the scan runs anywhere Docker runs, GitHub Actions included. Generate a rules file once with -g (every rule starts at WARN), change the rules you have fixed to FAIL, and commit it. A GitHub Actions job for a staging URL fits in ten lines:

jobs:
  zap-baseline:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v5
      - name: Passive ZAP baseline scan against staging
        run: |
          mkdir -p zap && cp .zap/rules.tsv zap/ && chmod -R a+w zap
          docker run --rm -v "$PWD/zap:/zap/wrk/:rw" -t ghcr.io/zaproxy/zaproxy:stable \
            zap-baseline.py -t https://staging.example.com -c rules.tsv -I -r report.html

The script exits with 1 when at least one rule set to FAIL fires, 2 when there are warnings and no FAILs, and 3 on any other failure; the -I flag stops warnings alone from failing the build, so only the rules you promoted to FAIL block a release. The chmod line is there because the container writes the report into the mounted folder. Keep zap/report.html as a build artifact.

Nuclei is the other open-source DAST tool worth knowing. ProjectDiscovery describes it as “A fast and customisable vulnerability scanner powered by simple YAML-based templates”, and its repository carries the MIT license. In my reading it suits a known check you want to run on purpose, where ZAP suits a crawl of the whole app. For open source web application security testing tools beyond these two, OWASP’s list of vulnerability scanning tools is the neutral index: its table has a License column, and ZAP, Nuclei and OpenVAS are listed as Open Source.

ZAP against Burp Suite, and ZAP’s automation framework, are covered under website security check. The baseline and full scan side by side belong to the vulnerability management tools a small team runs; here the full scan is only the active scan that goes on staging. Open source DAST means free to run; someone still has to read the report.

Dynamic application security testing tools: what to compare before paying

Dynamic application security testing tools differ on six things that matter to a small app: holding a login, crawling a JavaScript front end, importing an API definition, a passive-only mode, a pass or fail threshold for CI, and deduplicating findings between runs. Test those in a trial before comparing prices.

The six criteria are my working rule, and the list has no ranking. Searches for the best DAST tools often return lists published by DAST vendors; the best DAST tools for a small app are the dynamic application security testing (DAST) tools that pass all six on your own staging app.

Vendors sell DAST software under several labels, a DAST solution, dynamic application security testing software, DAST scanning tools, and the six checks apply whatever the label. PortSwigger calls Burp Scanner “an automated dynamic application security testing (DAST) web vulnerability scanner”. StackHawk now leads with “AI Coding Agent Security Platform” and lists “Modern DAST” among its use cases. GitLab’s DAST, which “runs automated penetration tests to find vulnerabilities in your web applications and APIs as they are running”, sits in its Ultimate tier. Run each of the DAST security tools you shortlist against staging, never production, and treat DAST testing tools that cannot pass the table as out.

For cloud apps and cloud environments, the best or leading dynamic application security testing tool is the one you would pick anywhere else; the cloud changes one thing, permission. AWS’s policy on security testing says customers “are welcome to carry out security assessments or penetration tests of their AWS infrastructure without prior approval for the services listed” under Permitted Services, and it still prohibits denial of service and request flooding. Your own host’s terms apply to a scan of an app on it. Vercel, Render and Supabase each publish one; Vercel’s says Pro and Enterprise customers can run non-volumetric penetration testing without notifying it in advance.

SAST vs SCA: your code against the code you imported

SAST vs SCA is your code against imported code. SAST reads what you wrote for risky patterns. SCA reads the manifest and lockfile and matches package versions against advisory databases. SCA starts from files you already have, and free tools such as Dependabot alerts, OSV-Scanner and OWASP Dependency-Check cover it.

The last column, and the SAST cell for the database behind it, are my reading. SCA vs SAST also differs in where the fix lives: an SCA finding is usually fixed by an upgrade, a SAST finding by an edit to your own code. Dependabot alerts fire when “a new vulnerability is added to the GitHub Advisory Database” or when your dependency graph changes, and OSV-Scanner “connects a project’s list of dependencies with the vulnerabilities that affect them”. OWASP Dependency-Check “identifies project dependencies and checks if there are any known, publicly disclosed, vulnerabilities”.

The usual SCA false alarm is an advisory for a function the app never calls. Deciding whether a CVE affects your app is its own question, and running the npm audit command is another.

Searches for SAST and DAST tools, or SAST/DAST/SCA tools, usually want one product that does all three. Platforms do bundle them: Snyk’s docs describe capabilities in SAST, DAST, SCA and infrastructure as code. For a small team, three free tools in one pipeline do the same job, in my reading; buying DAST, SAST tools and SCA as one bundle mostly saves you a dashboard. License checks are SCA’s other output, and OSV-Scanner “supports license checking as an official feature”. Whether you run SAST and SCA from one vendor or two, the order stays SCA, SAST: dependencies first.

What IAST is, and why a small team can skip interactive application security testing

IAST, interactive application security testing, typically places an agent inside the running app that observes it while tests exercise it, combining a DAST-style test with a view from inside the code. A small team can leave it for later: it needs a test suite that exercises the app, and an agent for your runtime.

NIST describes IAST tools as combining “elements of DAST with the instrumentation of the application under test”, with the agent watching “within the test runtime environment”. Interactive application security testing (IAST) tools ship as that agent, and NIST’s examples are the Java Virtual Machine and the .NET CLR, so the IAST tools you can use depend on your runtime. OWASP’s Developer Guide adds that IAST “provides instant feedback on the tests as they are run”.

IAST scanning and IAST security testing describe the same agent watching while something else drives the app, so an IAST test is only as good as the tests driving it.

That is why a small team can wait. At least 18 of the 21 third-party apps had no working test anywhere: 17 with literally none, plus a retail POS whose checkout “test suite” never executed the actual checkout code. Those 21 apps come from my June and July 2026 audits, a chosen group rather than a random draw, so the figures describe that group, not AI-built apps as a whole. IAST also needs an agent built for your runtime. In my reading the order is tests first, which pays off whether or not you ever buy an IAST tool.

IAST vs DAST: an agent inside against a scanner outside

DAST needs nothing installed in the app and sees only responses. IAST needs an agent in the runtime and tests running, and it watches from inside while they run. The difference between a DAST scan and an IAST scan is where the tool sits and what has to be in place before it can start. Which of the two finds more on a given app is not stated in the OWASP and NIST pages this article cites, so I make no claim either way.

When to pick each: the order a small team adds scans

A small team adds scans in a fixed order: dependency scanning on every pull request, a free SAST scan on every pull request, a passive DAST scan against staging before each release, then written tests and a person for what no scanner sees, such as one customer reading another’s data.

The order is my working rule, and it follows OWASP’s basic pipeline list, where SCA and SAST come before IAST and DAST. The per-change routine that goes with it, baselines, suppressions and what to record for each result, lives in the scanner article linked in the DAST section.

First: SCA on every pull request

SCA fits every app, because every app imports code. Turn on Dependabot alerts, which scan your repository’s default branch, and run OSV-Scanner as a CI step so a pull request that adds a vulnerable package is caught before merge. My working rule is to fail the build only on new high-severity advisories with a fix available. SCA does not fit as the only control: it says nothing about the code you wrote.

Second: SAST on every pull request

GitHub code scanning with CodeQL is available for public repositories on GitHub.com, and you turn it on in the repository’s settings with CodeQL’s default setup. On a private repository it needs GitHub Code Security, which you can only buy on a GitHub Team or GitHub Enterprise plan, as GitHub’s page on GitHub Advanced Security explains. Semgrep Community Edition runs anywhere: its engine is open source under LGPL 2.1, and Semgrep’s maintained rules are licensed for internal business use. My working rule is to block on new high-severity findings only, so old noise doesn’t stop every merge. SAST does not fit as proof of anything about the deployed app.

Third: a DAST baseline scan against staging before each release

Start passive: the baseline scan doesn’t perform attacks, and ZAP describes passive scanning as “considered safe”, so it can run before every release. My working rule is that active scans run only on staging, with seeded test data and a throwaway account, because ZAP describes active scanning as an attack on the target. That keeps the full scan away from real customers. No scan of this kind fits on a system you do not own, and for active scans ZAP’s own page says so in as many words.

After that: written tests for what no scanner sees, then a person

Two tests cover the rows no scanner supports. The first signs in as two users and has one try to read, change and delete the other’s records. The second replays a payment or webhook request and checks that nothing is charged or granted twice. After those, the next step is a targeted test by a person, which is a different purchase. Doing one is covered in web application penetration testing, how it differs from an assessment is in pen test vs vulnerability assessment, and whether a customer actually requires one is answered in do I need a pen test. A native client changes the list; see mobile app security best practices.

How to run a first DAST scan safely, and read what it says

A first DAST scan is safe when you own the target, the host’s testing policy allows it, it points at staging, it starts passive, a planted missing header proves it reaches the app, every finding is sorted into fix, accept or false positive, and the report is kept.

These steps hold for ZAP’s baseline scan run from its official Docker image, against a staging URL you control, on a host whose testing policy allows it.

1. 01 Confirm you own the target, then read your host's policy on security testing. Save the link and the date you read it.
2. 02 Point the scan at staging, never at a third party's domain, and tell whoever watches your alerts before it runs.
3. 03 Run the baseline scan from the official ZAP image and keep the report file.
4. 04 Prove the scan reaches the app: remove one security header your app sets, such as X-Content-Type-Options, redeploy staging, confirm with curl -I that the header is gone, and re-run. The report should now show X-Content-Type-Options Header Missing. Restore the header and confirm the alert is gone. A scan that misses the plant is not reaching the app, or its passive rules are off.
5. 05 Read the report by risk (High, Medium, Low, Informational) and by confidence, and sort every item into fix, accept with a written reason, or false positive.
6. 06 For each category the report touches, test it properly rather than trusting the scan alone.
7. 07 Wire the scan to run before each release with the rules you fixed set to FAIL, and keep the last three reports (my working rule). Never run an active scan against production, a payment provider, an auth provider or any address you do not control.

The alert name in step 4 comes from ZAP’s alert list, where X-Content-Type-Options Header Missing is rule 10021, a passive rule rated Low. If your host adds that header itself, removing it from the app changes nothing, so plant a different one your app controls. Step 6 has its own guide, how to test OWASP Top 10 vulnerabilities, which goes category by category.

In the Production Hardening Sprint, deliverable 3.4, production security headers, is verified this way: inspect response headers and exercise the application to confirm intended protections without broken flows.

Where the sprint fits

Four more sprint deliverables touch the scans on this page. Deliverable 3.5 audits dependencies, upgrades or removes known-vulnerable packages, and removes unused packages. For 3.7, we review the application against the OWASP Top 10 and record findings, fixes, and evidence by category. Deliverable 7.3 runs linting, type checks, builds, and tests on every pull request. Under 3.10, we test the five highest-risk externally reachable attack surfaces, remediate findings, and deliver the methods and evidence, because implementation review alone may miss behavior exposed through real attack paths. Formal third-party certifications and independent audit opinions are separate from the sprint deliverables. Hosting, paid tools, and API usage remain in the client’s own accounts. Every deliverable is listed in the published scope.

Common questions about security scan types

Which is better, SAST or DAST?

Neither on its own, because they read different things: SAST reads your source code and DAST exercises the running app. My working rule is SAST on every pull request and a passive DAST scan before each release. None of the sources this article cites ranks one above the other.

Are DAST and Vapt the same?

No. VAPT is a services label, short for vulnerability assessment and penetration testing, while DAST is one automated technique an assessment may use. A penetration test adds a person reasoning about your app’s logic, which no scanner does; how the two services differ has its own page on pen tests against vulnerability assessments.

Is DAST a vulnerability scan?

Yes, one kind. DAST scans a web app’s behavior from outside, while network vulnerability scanners check hosts and services. OWASP’s scanning tools list mixes both, with web scanners such as ZAP beside broader scanners such as OpenVAS.

Is OpenVAS free to use?

Yes. OpenVAS is part of the Greenbone Community Edition, which Greenbone says “is released under open-source licenses”, and the scanner can use “the free available Greenbone Community Feed” instead of the commercial Greenbone Enterprise Feed. Details are in Greenbone’s community documentation. It is a network vulnerability scanner, not a web-app DAST tool.

Is Nessus still free?

Only in a narrow form. Tenable describes Nessus Essentials as “a free product” with “a 30-day license, designed specifically for non-commercial or personal use”, and says it can scan “up to 5 IPs”; commercial use needs a paid Nessus Professional license. Like OpenVAS, it scans hosts rather than acting as a web-app DAST tool.

Is Snyk SAST or DAST?

Both, through different products. Snyk’s glossary calls Snyk Code “A SAST product”, Snyk Open Source finds “open-source vulnerabilities” (that is SCA), and Snyk API & Web tests running APIs and web apps, which is the DAST side.