The Best Free Tools to Check if a Business Has Been Compromised

• BizVuln Expert

Discover a curated list of the best free tools to check if a business has been compromised, from breach databases and dark web monitors to domain reputation scanners and exposed service detectors. Essential reading for security consultants, MSSPs, and business owners who need fast, no-cost visibility into their organization's security posture.

The Best Free Tools to Check if a Business Has Been Compromised

In today’s threat landscape, the question is no longer if a business will be targeted, but when and how often. For security consultants, MSSPs, and business owners, the ability to rapidly assess whether an organization has already been compromised—through leaked credentials, exposed assets, or active malware—is a critical first step in any engagement or internal review. While paid threat intelligence platforms offer deep visibility, there is a powerful arsenal of free tools that can surface alarming indicators of compromise without a single dollar spent.

This guide walks through the most effective free resources available today, categorized by the type of threat they uncover. Each tool is evaluated for its reliability, ease of use, and the specific value it brings to a professional security assessment.

Why Free Tools Matter (and Where They Fall Short)

Free tools democratize security intelligence. They allow small consultancies, internal IT teams, and budget-conscious business owners to perform baseline compromise checks without vendor lock-in. However, they should not be mistaken for comprehensive threat hunting platforms. Free tools often have rate limits, delayed data, or limited historical scope. When used together, though, they create a surprisingly robust initial triage process.

For an MSSP deploying a solution like BizVuln, these free tools complement automated scanning by providing human-readable context and external validation. Use them as a starting point—then feed findings into your broader vulnerability management workflow.

1. Credential Leak & Breach Databases

Have I Been Pwned (HIBP)

URL: haveibeenpwned.com

Troy Hunt’s HIBP is the gold standard for checking if business email addresses or domains appear in known data breaches. Enter a corporate domain (e.g., @bizvuln.com) to see all associated email addresses that have been exposed. The service now supports domain-level searches, which is invaluable for MSSPs auditing an entire organization.

Firefox Monitor

URL: monitor.firefox.com

Powered by HIBP data, Firefox Monitor offers a cleaner interface for tracking multiple email addresses. Businesses can get alerts when new breaches affect their domains. It’s especially useful for non-technical business owners who want automated notifications without API complexity.

DeHashed

URL: dehashed.com

While DeHashed has a paid tier, its free search lets you look up email addresses, usernames, and IPs against a vast database of breached credentials. Results include plaintext passwords (when available), which is a severe indicator of compromise. For a quick “is this account compromised?” check, DeHashed is indispensable.

2. Domain & Email Reputation Tools

Google Safe Browsing

URL: transparencyreport.google.com/safe-browsing/search

Check if a domain is flagged for malware, phishing, or unwanted software. Enter any URL to see Google’s verdict. This is the first line of defense for a business owner who wants to know if their website is being used as a distribution point for malware.

VirusTotal

URL: virustotal.com

Beyond file scanning, VirusTotal’s domain and URL analysis aggregates results from 70+ security vendors. Search a business domain to see if any scanners detect malicious activity, phishing, or botnet associations. The community comments section often reveals historical compromise data.

URLScan.io

URL: urlscan.io

Take a live snapshot of any website and analyze its behavior. URLScan records redirects, JavaScript execution, and contacted domains. For a compromised business, you might see the site loading malicious scripts from a C2 server. The free tier allows up to 50 scans per month, sufficient for manual triage.

3. Exposed Services & Surface Monitoring

Shodan

URL: shodan.io

Shodan scans the internet for open ports and services. Searching for a business’s IP range reveals exposed databases (MongoDB, Elasticsearch), unsecured RDP, or even default credentials on IoT devices. A compromised business often shows unexpected open ports, misconfigured services, or banners that leak internal information.

Censys

URL: search.censys.io

Similar to Shodan but with a focus on certificates and detailed TLS metadata. Censys can uncover expired or misissued SSL certificates that attackers might exploit, or show you every public-facing asset of a company. The free tier is generous and includes historical data.

GreyNoise

URL: greynoise.io

GreyNoise differentiates internet noise (scanners, crawlers) from targeted attacks. Search an IP to see if it’s associated with known threat actors or vulnerability scanners. If a client’s internal IP appears in GreyNoise with malicious tags, it suggests a compromised device is communicating outbound.

4. Dark Web & Forum Monitoring (Free Tiers)

Intelligence X

URL: intelx.io

Intelligence X provides a free search across dark web markets, paste sites, and document leaks. Enter an email, domain, or IP to find mentions in illicit dumps. Results often include full credential pairs, private key leaks, or database exports.

Ahmia.fi

URL: ahmia.fi

A search engine for .onion sites. While not exclusively for breach data, it can surface hidden services that discuss or sell company data. Use with caution—simply browsing .onion sites carries legal risk in some jurisdictions.

SpyCloud (Free Identity Check)

URL: spycloud.com/identity-check

SpyCloud offers a one-off free scan of up to 10 email addresses to reveal exposed credentials from malware stealer logs and breaches. It’s particularly valuable because it includes data from infostealer-infected devices, which HIBP does not always cover. For an MSSP, this can quickly show if a client’s passwords are circulating in current criminal markets.

5. DNS & Certificate Transparency

crt.sh

URL: crt.sh

Certificate Transparency logs record every SSL/TLS certificate issued for a domain. Search %.bizvuln.com to see every subdomain that ever had a certificate—including expired ones. Attackers often create lookalike domains or get certificates for test subdomains; crt.sh can reveal unauthorized certificates or forgotten assets.

SecurityTrails

URL: securitytrails.com

SecurityTrails offers free DNS history, reverse IP lookups, and subdomain discovery. If a business has been compromised through a third-party service or forgotten subdomain, this tool makes it visible. The free tier allows 50 queries per month.

6. Phishing & Typosquatting Detection

PhishTank

URL: phishtank.com

Search a domain to see if it has been submitted as a phishing site. If a lookalike domain (e.g., bizvuIn.com with a capital i) is reported, it indicates an active impersonation campaign against the business.

DNSTwister

URL: dnstwister.report

Enter a domain to generate hundreds of potential typosquatting domains. The tool checks which are registered and provides a threat score. For an MSSP, this is a quick way to show a client how many fake domains are targeting their brand.

OpenPhish

URL: openphish.com

OpenPhish maintains a feed of active phishing URLs. While the full feed is paid, the free lookup allows you to check individual URLs or domains. Use it to verify whether a suspicious link sent to your client is part of a known campaign.

7. Malware & Botnet Feeds

AbuseIPDB

URL: abuseipdb.com

Check an IP address against community-reported abuse reports. If a business’s public IP appears repeatedly for SSH brute-force or malware distribution, it suggests a compromised server or infected internal host. Free API access (1,000 lookups/day) makes it suitable for bulk checks.

ThreatMiner

URL: threatminer.org

A free threat intelligence portal that aggregates data from multiple sources. Enter a domain, IP, or hash to see relationships with known malware families, C2 servers, and other indicators. It’s more research-oriented, but extremely valuable for deep dives.

AlienVault OTX (Open Threat Exchange)

URL: otx.alienvault.com

OTX allows you to search a domain or IP against millions of threat indicators submitted by the community. The pulses feature shows context: “This IP was seen connecting to a ransomware C2 in the last week.” Free account gives full API access.

8. Putting It All Together: A Practical Workflow for MSSPs

Using these free tools in a systematic way can yield a powerful initial compromise assessment. Here’s a recommended sequence:

  1. Domain & Credential Check: Run the business domain through Have I Been Pwned and SpyCloud. Note any exposed emails and passwords.
  2. External Asset Discovery: Search the domain on SecurityTrails and crt.sh to find all subdomains and digital assets. Check each on Shodan or Censys for open ports or misconfigurations.
  3. Reputation Scan: Query the primary domain on VirusTotal, Google Safe Browsing, and URLScan.io to identify active threats.
  4. Dark Web Sweep: Search key emails and the domain on Intelligence X and DeHashed for any mention in breach dumps or paste sites.
  5. Phishing & Typo Hunting: Use DNSTwister and PhishTank to find malicious lookalike domains or ongoing phishing campaigns.
  6. IP & Infrastructure Check: Run all discovered IPs through AbuseIPDB, GreyNoise, and OTX to see if they are flagged for malicious activity.

Document every finding, especially confirmed credentials in plaintext, active C2 connections, or unsecured databases. These are immediate items for your remediation plan.

Critical Caveats for Professionals

Free tools are powerful but have limitations that a professional must acknowledge:

For an MSSP, integrating these free checks into a preliminary assessment can justify the need for a more robust solution like BizVuln, which automates continuous monitoring and correlates findings across multiple threat feeds.

Conclusion

Knowing whether a business has been compromised doesn’t require a six-figure threat intelligence platform. The free tools listed above—when used with a clear methodology—can reveal credential leaks, exposed systems, active phishing campaigns, and dark web chatter. For security consultants and MSSPs, they serve as a rapid triage mechanism that builds trust with clients and underscores the importance of ongoing vigilance.

Start your next engagement with this checklist. Show your client exactly what attackers can see about them for free—and then demonstrate how a proactive security program (including BizVuln’s automated vulnerability scanning and threat intelligence) closes those gaps before they become incidents.

The best compromise check is the one you perform before the attacker does.