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Best Practices for Reducing Your External Attack Surface

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Best Practices for Reducing Your External Attack Surface

Scanning & DetectionDuration7 min

Introduction​

An organization’s external attack surface includes all the publicly accessible systems, services, and applications that attackers can target. Reducing your attack surface minimizes these potential entry points, making it harder for attackers to exploit vulnerabilities.

This article outlines best practices to effectively manage and reduce your attack surface, ensuring a stronger security posture.

Why Attack Surface Reduction Matters​

The Risks of a Large Attack Surface​

A wide attack surface increases the chances of:

  • Exploitable vulnerabilities in exposed assets.
  • Misconfigurations that provide attackers with easy access.
  • Shadow IT (systems outside of IT’s knowledge or control).

The Benefits of Minimizing Exposure​

Reducing your attack surface:

  • Lowers the likelihood of breaches.
  • Simplifies vulnerability management by focusing on fewer assets.
  • Improves compliance with security frameworks like NIST or CIS.

Best Practices for Reducing Your Attack Surface​

1. Perform Regular Asset Discovery​

Keep an up-to-date inventory of all external assets, including:

  • Domains and subdomains.
  • Public-facing IPs and ports.
  • Cloud services and third-party integrations.

2. Monitor for Shadow IT​

Identify and manage unauthorized systems and services:

  • Scan for unapproved cloud instances or SaaS tools.
  • Audit DNS and SSL configurations for unknown subdomains.

3. Restrict Open Ports and Services​

Minimize exposure by:

  • Closing unnecessary ports (e.g., RDP, Telnet).
  • Disabling unused services on public-facing servers.
  • Configuring firewalls to restrict access to sensitive systems.

4. Apply Strong Authentication Controls​

Ensure all external-facing services are secured with:

  • Multi-Factor Authentication (MFA).
  • Strong password policies.
  • Certificate-based authentication where applicable.

5. Patch and Update Regularly​

Stay ahead of vulnerabilities by:

  • Applying software updates as soon as they’re available.
  • Monitoring for zero-day exploits and acting quickly.

6. Decommission Unused Assets​

Remove assets no longer in use, such as:

  • Legacy domains and subdomains.
  • Deprecated web applications or APIs.
  • Dormant cloud instances.

7. Monitor Certificate Transparency Logs​

Track SSL certificates to:

  • Identify unauthorized or unexpected subdomain registrations.
  • Ensure all certificates are valid and up-to-date.

8. Enforce Network Segmentation​

Separate public-facing systems from internal networks to:

  • Contain potential breaches.
  • Limit the blast radius of successful attacks.

Common Mistakes to Avoid​

Ignoring Low-Severity Issues​

Even low-severity vulnerabilities can escalate if left unaddressed, especially as part of a chain of attacks.

Overlooking Third-Party Risks​

Third-party services and integrations can introduce vulnerabilities outside your direct control. Regularly review and manage these connections.

Infrequent Asset Audits​

Assets and configurations change over time. Failing to audit regularly can result in missed risks.

Frequently Asked Questions

AI-Powered Insights
Can I ask follow-up questions about vulnerabilities?

Absolutely! The 'Dig Deeper' chat is interactive, allowing you to:

  • Request more details about how a vulnerability works.
  • Ask for additional remediation methods.
  • Clarify attack vectors and potential risks.

This ensures security teams get deeper insights beyond just a vulnerability description.

What is the 'Dig Deeper' chat, and how does it help?

The 'Dig Deeper' AI chat provides instant expert-level insights on detected issues.

  • It explains vulnerabilities in a clear, actionable way.
  • It helps users understand why an issue is risky and how attackers might exploit it.
  • It suggests remediation steps tailored to the asset and issue type.

This allows security teams to quickly grasp risks and respond effectively without deep security expertise.

Access & Security
Does this tool comply with security frameworks like NIST or CIS?

Yes, the EASM tool aligns with frameworks such as NIST, CIS, and ISO 27001 by identifying security gaps in publicly accessible infrastructure. While it does not enforce compliance, it helps security teams detect misconfigurations and vulnerabilities that could impact regulatory requirements.

Scanning & Detection
What sources does the scanner use to find vulnerabilities?

The scanner leverages multiple intelligence sources to detect vulnerabilities, including:

  • Public vulnerability databases (CVE, NVD, MITRE, etc.).
  • Security research feeds and threat intelligence sources.
  • Passive reconnaissance techniques such as OSINT and fingerprinting.

By combining these sources, the scanner provides real-time risk assessments without intrusive scans.

Does the scanner perform active exploitation or just passive mapping?

The scanner performs only passive mapping, meaning it identifies vulnerabilities but does not exploit them.

This approach:

  • Avoids system disruptions while gathering security intelligence.
  • Provides safe, real-world attacker perspectives without breaching legal boundaries.
  • Ensures compliance with ethical scanning practices.

Organizations can use these findings to proactively patch weaknesses before attackers do.

How does the EASM scanner find subdomains?

The scanner discovers subdomains using:

  • DNS enumeration (brute-force, dictionary-based, wildcard resolution).
  • Certificate transparency logs that expose registered subdomains.
  • Passive DNS records and web crawling to identify related assets.

This helps map the full attack surface, including shadow IT and forgotten subdomains.

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