One platform.
Relevant checks.
Free scans. AI-powered analysis. Continuous monitoring. Browser extension. 12,000+ security checks. All in one place.
Outside, continuous,
and inside.
External Scanning
Manual scans of your internet-facing assets, from the outside, like an attacker.
AI-based CTEM
S4E keeps watching: continuous scanning, prioritised actions and AI fix guidance.
Credentialed Scanning
Add a server login and S4E also looks inside the server for outdated, vulnerable software.
A library of 12,000+ focused, single-purpose scans targeting specific CVEs, technologies, and configuration weaknesses. Every feature on this page is powered by this engine.
New CVEs, covered
within hours.
S4E monitors the global vulnerability landscape daily and ships scanner support as new CVEs emerge so your assets are checked before attackers can exploit them.
See all CVE scanners →Describe it.
AI scans it.
No coding needed. Describe what you want to test the AI generates the exact code, executes it on the S4E engine, and delivers real-time results you can review, tweak, and re-run.
Check if our checkout page leaks card data to 3rd-party scripts, and verify session tokens expire after password reset.
I've generated a targeted scan based on your requirements. Here's what I created:
import requests from bs4 import BeautifulSoup def check_pci_leak(url): """Check outbound requests for PCI data""" resp = requests.get(url, timeout=10) soup = BeautifulSoup(resp.text, "html.parser") scripts = [ src["src"] for src in soup.find_all("script", src=True) ] return { "third_party": scripts, "risk": "HIGH" if len(scripts) > 5 else "LOW" }
Scans that
never stop.
Schedule recurring scans across your entire attack surface. The Scheduler runs 24/7: new subdomains, expired certificates, open ports, fresh CVEs, and newly vulnerable packages inside your servers when Inside depth is on. You get notified, not surprised.
Start continuous monitoring →The attacker's view,
and the sysadmin's.
Every Full Scan starts with Outside depth: the services and web app the internet can see. Turn on Inside depth and the same scan signs in over SSH or WinRM, reads the installed packages and OS, and matches them against vendor advisories. No agent to install.
Credentials live on the asset, under Access, and connecting also verifies the asset. Built on Openness, S4E's open source host scanner.
How Inside depth works →Scan from anywhere,
see everything in one place.
Servers behind your firewall need a scanner inside the firewall. The S4E Connector is a small docker compose you run in your network. It connects outbound only, enrolls with a token from the UI and updates itself. Findings land in the same console as everything else. Pro includes one Connector, Enterprise has no limit.
About the Connector →Security intel,
always one tab away.
Install the S4E extension and scan from the tab you're already on. Save your session for authenticated web scans, collect attack surface as you browse, and set crawl include/exclude rules without leaving the page.
Add to Chrome Free →Plug S4E
into your stack.
REST API, MCP protocol, webhooks, CI/CD pipelines. Build security into your workflow programmatically trigger scans, consume results, and automate remediation.
Read API docs →REST API
Full programmatic access to scans, results, assets, and reports.
MCP Protocol
Connect S4E to AI agents and LLM workflows as a tool provider.
CI/CD
Run security checks in your deployment pipeline. Block on critical findings.
Built with the community.
Tools we build and maintain, projects we sponsor, and services that extend the S4E ecosystem.
Openness
GitHubOpen source host scanner, developed and maintained by S4E. A collector reads the software installed on a Linux or Windows server, a resolver matches it against vendor advisories. Inside depth in S4E builds on it.
Explore Openness →Spark
GitHubReal-time security alert client. Monitors your assets continuously and fires notifications the instant a new vulnerability appears, a port opens, or a certificate expires.
View on GitHub →Playbooks
GitHubPre-built scan sequences for compliance, pentest, and reconnaissance. PCI-DSS, ISO 27001, full attack surface mapping select a goal, hit run, S4E does the rest.
View on GitHub →Labs
Open SourceNuclei top contributor, Wapiti sponsor, Openness collector and resolver, open access research, whitepapers and anonymized data for the security community.
Explore Labs →Start free.
Scale when ready.
No credit card. No commitment. Just sign up and scan.