Attack Surface Reduction: Best Practices and Examples

Your organization's attack surface is the complete sum of all the potential entry points where an unauthorized user can attempt to penetrate your environment and extract data. Think of it as the total exposed area of your business that an attacker could exploit.

This surface isn't just limited to your physical infrastructure; it comprises three core areas:

• Digital assets: Everything connected to the internet, including network ports, web applications, APIs, cloud environments, public-facing servers, and software code.
• Physical assets: Endpoints, IoT devices, and physical access points like server rooms.
• Human elements: Employees and third-party vendors who possess credentials or access to sensitive systems.

A larger attack surface creates a direct and proportional relationship with higher cyber risk. Each exposed asset, open port, or unnecessary user account is an attack vector—a potential path for a threat actor to compromise the system, ultimately increasing the likelihood and potential impact of a data breach.

This guide expands on the strategic imperative of attack surface reduction, its framework integration. It provides you with practical strategies and examples to help you further compress your attack surface and reduce threat exposure.

Learn how UpGuard streamlines attack surface management >

Practical Strategies for Attack Surface Reduction

Attack Surface Reduction (ASR) is a continuous, systematic process that requires a coordinated effort across your entire organization. The goal is to minimize the total area that must be defended by eliminating unnecessary assets and hardening the remaining essential ones. The following steps provide a hands-on, strategic guide to achieving meaningful attack surface compression.

Step-by-step guide to strategic ASR

For any ASR effort to succeed, you must first achieve complete asset visibility; you can’t reduce what you can’t see. This process requires a shift in thinking from reactive security (fixing vulnerabilities on known assets) to proactive exposure management (finding and securing everything an attacker can see).

Step 1: Discover and document all assets (Continuous Asset Discovery)

The attack surface encompasses both known assets (tracked in your IT inventory) and unknown assets, also known as Shadow IT (unauthorized or forgotten systems). Hackers specifically target these blind spots because they are often unpatched and unsecured.

• Action: Use automated asset discovery tools to continuously scan your network and the internet for all associated domains, IP addresses, web applications, and cloud resources.
• ASR goal: Eliminate blind spots. Establish a dynamic inventory that accurately reflects everything exposed to the public internet.

Step 2: Eliminate unnecessary exposure

This step is the most literal form of attack surface reduction—physically removing attack vectors.

• Cull services and ports: Identify and shut down any unused services or network ports that aren’t strictly necessary for business operations. For instance, turn off older, vulnerable protocols or administrative ports exposed to the public internet.
• Decommission legacy systems: Immediately retire or isolate any legacy software or outdated hardware that cannot receive the latest security patches. If decommissioning isn't possible, apply strict controls or virtual patching to these systems.
• ASR goal: Physically shrink the digital footprint, leaving fewer pathways for initial access.

Step 3: Enforce the principle of least privilege (PoLP)

PoLP is a core element of Zero Trust, focusing on limiting the damage an attacker or compromised credential can do by restricting access.

• Review and restrict user access: Regularly audit and remove any unnecessary user privileges or accounts, especially administrative rights. Implement Role-Based Access Control (RBAC) to ensure that users have only the permissions necessary for their specific job functions.
• Limit third-party access: Systematically review and reduce the access privileges granted to third-party vendors, suppliers, and contractors to ensure a secure environment. Third-party connections represent a significant supply chain attack surface, so access should be the minimum required and monitored continuously.
• ASR Goal: Reduce the human attack surface and limit the potential for an attacker to move laterally using compromised credentials.

Step 4: Segment and contain risk

Network segmentation prevents a successful breach of one system from compromising the entire network.

• Implement microsegmentation: Divide your network into smaller, isolated zones (e.g., separating customer data, financial systems, and development environments). Use firewall rules or security policies to control the traffic flow between these zones strictly.
• ASR goal: Contain threats and prevent an attacker from achieving lateral movement (moving east-west across the network) even after gaining initial access to a single point.

Step 5: Maintain and harden remaining assets

For every essential asset that remains, you must ensure it is configured securely, which involves ongoing patching and configuration management.

• Patch management: Keep all operating systems, firmware, and applications up to date with the latest security patches. This benefits from the security investments made by third-party providers.
• Harden configurations: Eliminate default configurations that leave systems exploitable, such as default passwords or open services. Secure public-facing cloud services by addressing common misconfigurations, such as overly permissive Amazon S3 buckets or open security groups.‍
• ASR goal: Harden the remaining surface area against known exploits and common configuration errors.

Cross-functional collaboration for ASR

ASR isn't solely the job of the security team. It requires orchestration among different departments:

Attack surface management (ASM) vs. traditional vulnerability management (VM)

While the terms are often confused, Attack Surface Management (ASM) and Vulnerability Management (VM) serve complementary roles in risk reduction, each playing distinct roles.

ASM insights drive ASR. ASM provides the necessary visibility to reduce the number of systems and services exposed, and VM then ensures those remaining assets are updated and secured.

18 practical examples of attack surface reduction

1. Identify assets that don't need to be connected to the internet

Disconnecting unnecessary devices and systems from the internet can reduce the risk of cyberattacks. This includes limiting the number of integrations, web servers, interfaces, and IP addresses exposed to potential threats.

You can identify devices that could be culled from your attack surface by referring to your IT inventory. With a strong Shadow IT policy, this document should accurately reflect all approved devices in your attack surface. However, outside of a CISO's idealistic world, there will always be a discrepancy between an organization's IT inventory and its actual attack surface. 

This is why attack surface reduction processes should augment attack surface management solutions that identify all IP addresses associated with your attack surface. Besides endpoints, these discoveries could include domains associated with vulnerable server software increasing your risk of suffering a data breach.

Watch the video below for tips on how to quickly reduce your attack surface.

‍‍Request a free trial of UpGuard >

2. Secure all Mobile Devices and Implement a Strong Device Policy

Establish a policy that details security protocols for device usage, including encryption requirements, approved applications, and mandatory use of VPN when connecting to public Wi-Fi. Also, consider implementing Mobile Device Management (MDM) solutions to control, enforce, and protect the organization's data on these devices.

Lean how to choose an external attack surface monitoring tool >

3. Address Misconfigurations and Vulnerabilities

Detected vulnerabilities are the clearest indication of an excessive attack surface region that should be culled. A vulnerability scanner can automatically assess all of the domains and devices within your attack surface that contain exploitable security vulnerabilities.

An example of a vulnerability scanner is a security rating solution that quantifies security postures based on commonly exploited attack vectors and other unbiased factors.

‍Learn how UpGuard calculates security ratings >

4. Monitor for Shadow IT

Unapproved software and hardware introduce significant security risks to your organization. Use automated asset discovery tools to detect unauthorized software or hardware on your network. Implementing a streamlined process for requesting new software or hardware connections could be a quick solution to most Shadow IT instances.

5. Restrict USB Usage

In addition to seeking approval for connecting new USB devices, implement a policy that requires encryption for any data transferred from USBs. Also, consider disabling auto-run features for USB drives to prevent any potential malware from automatically executing.

6. Secure Access Points and Implement Zero Trust Architecture

Employee accounts are keys to a private network, and without proper account security controls in place, they become excessively bloated regions of your attack surface. Multi-Factor Authentication (MFA) is one of the easiest and most effective methods of protecting an account from most compromise attempts. 

To mitigate lateral network movement should hackers find a way of exploiting MFA, a Zero-Trust architecture should be implemented. A Zero-Trust architecture is like extending MFA across all regions of your private network. With Zero-Trust, all users and devices are required to continuously authenticate themselves to justify their access to a network.

Learn how to implement a Zero-Trust architecture >

7. Conduct Attack Surface Analysis

Regularly perform attack surface assessments to identify potential vulnerabilities and areas for improvement. This should not be a one-time activity but a regular practice. Use automated tools to continuously monitor your attack surface and identify new risks as they emerge.

‍Learn how UpGuard streamlines attack surface management >

8. Implement Attack Surface Reduction Rules

Use tools like Group Policy and Intune to enforce security policies that minimize your organization's attack surface. Ensure these rules cover user behavior, system configuration, and network connections.

9. Manage Permissions and User Access

Regularly review user permissions and implement the principle of least privilege, which limits users' access to only the resources necessary for their job functions. Implement a system that provides regular reports on user permissions and flags any excessive or abnormal permissions for review. Consider implementing Role-Based Access Control (RBAC) to streamline user permissions management.

10. Secure Physical Attack Surface

Implement measures to protect against physical threats, such as unauthorized access to data centers or server rooms.

11. Address Potential Vulnerabilities in Web Applications and Servers

Regularly test and update web applications and servers to minimize the risk of unauthorized access and data breaches. This will involve Implementing physical security measures such as surveillance cameras, biometric access controls, and alarm systems. 

Since these devices will inevitably expand your attack surface, they should be carefully assessed against your risk appetite to ensure their risk exposure doesn't outweigh their attack mitigation benefits.

12. Implement Strong Password Policies

Require users to create complex and unique passwords to prevent account compromise due to weak passwords. To eradicate the risk of weak passwords, use password management solutions that generate, store, and autofill complex passwords; and educate users on the importance of not reusing passwords across different systems.

Get your free password security checklist >

13. Educate Employees about Social Engineering & Phishing

Train employees to recognize and avoid phishing attacks - one of the most common initial attack vectors leading to data breaches and ransomware attacks. These types of attacks target credentials for beaching any gateways on the digital attack surface. These could include firewalls, VPNs, and even security teams operating systems, such as antivirus software, Microsoft Defender, and vulnerability management programs.

Regularly conduct simulated social engineering and phishing attacks to test employee resilience against evolving tactics. With the support of ChatGPT, you can establish an in-house phishing simulation program at a fraction of the cost of hiring a third-party service. Read this post to learn how.

Your ransomware attack surface can be further reduced by scanning the dark web for evidence of sensitive data dumps following a ransomware attack. This specific disciple of data leak detection is known as ransomware blog data leak detection, because ransomware gangs usually publish details about stolen data on their ransomware blogs.

Learn how to defend against ransomware attacks >

14. Adopt the Principle of Ongoing Attack Surface Management

Following the successful detection and remediation of detected cyber risks, Implement a mechanism for continuously monitoring evolving security threats, both internally and throughout the third-party network.

Ongoing monitoring is a tenet of Vendor Risk Management, a cybersecurity discipline with increasing emphasis across regulations.

15. Implement Network Segmentation

Divide your network into smaller segments to reduce the potential of sensitive data compromise if your network is breached. Segmentation rules should be regularly reviewed as your network evolves. 

To check whether a network has been sufficiently segmented, have penetration testers attempt to access the sensitive network regions they're designed to obfuscate.

Learn the top network segmentation best practices >

16. Regularly Patch and Update Software and Hardware

Keeping all software, firmware, and hardware up-to-date with the latest security patches is one of the easiest methods of addressing the security risks of third-party solutions. It costs you nothing and allows you to benefit from the cybersecurity investments of your third-party providers.

17. Develop an Incident Response Plan

Create a comprehensive incident response plan outlining the steps to be taken during a security breach. This should include communication protocols, roles and responsibilities, and recovery procedures. A well-designed IRP will shut down active cyber threats before they have a detrimental impact on your sensitive resources - helping you achieve an outcome that's equivalent to a smaller attack surface.

Regularly conduct drills to test the response plan's execution time and make necessary improvements based on feedback from these drills.

Learn how to create an incident response plan >

18. Perform Regular Security Audits and Penetration Testing

Penetration tests will uncover any gaps in your security control strategy that represent excessive attack surface exposure. To remove the risk of bias, these tests should be performed by independent third parties. Penetration tests should be performed regularly to ensure your attack surface is kept minimal at all times.  

Remember, all penetration tests should be considered successful - those that fail to compromise your data and those that succeed. A successful simulated breach is an opportunity to secure a potential pathway before a real hacker discovers and exploits it.

Tools and techniques for continuous monitoring

Attack surface reduction is only effective if it's sustained. In today’s dynamic environment—where new cloud instances spin up in minutes and third-party vendors are onboarded weekly—relying on manual, periodic security reviews is a recipe for disaster. This is where automation and Continuous Attack Surface Management (CASM) become essential tools for shrinking risk.

The role of automation and continuous monitoring

Continuous monitoring is the practice of automatically and persistently scanning an organization’s IT infrastructure and external-facing assets for exposures, threats, and misconfigurations in near real-time.

• Necessity in dynamic environments: Manual, point-in-time scans quickly become outdated, leaving security teams blind to new risks created by rapid development cycles (DevOps), containerization, or simple human error. Automated tools eliminate this loophole by detecting changes the minute a resource appears.
• Automation in practice: CASM tools use automation to handle the tedious work of continuous asset discovery, data aggregation, and correlation. This enables security teams to move from being reactive investigators to strategic remediators, focusing their limited resources on the most critical exposures. When an issue is found, these platforms can automate alerts and integrate with existing ticketing or workflow systems, such as JIRA or ITSM, to ensure vulnerabilities are reported directly to the appropriate team for rapid fix.

This continuous feedback loop—often incorporated into a constant threat exposure management (CTEM) program—ensures that visibility translates into actionable, prioritized defense.

Key Features in ASR and ASM tools

When evaluating solutions to help implement your Attack Surface Reduction strategy, look for platforms that offer:

• External attack surface management (EASM): This is the ability to scan and analyze your digital assets from an attacker’s external perspective. EASM identifies public-facing entry points, unknown systems (Shadow IT), and cloud misconfigurations that might otherwise be invisible to internal tools.
• Real-time alerts and visibility: A critical feature is the ability to generate an immediate alert upon the discovery of a new, unmanaged asset or a critical configuration change (known as "configuration drift"). Real-time visibility ensures the time between deployment and identification is kept to a minimum.
• Risk Scoring and prioritization (security ratings): Security teams often identify more vulnerabilities than they have resources to fix quickly. Practical tools use a risk-based approach to assign a quantified risk score or security rating to each exposure. This process prioritizes remediation activities based on factors like exploitability, asset criticality, and the severity of the associated threat, guiding teams to focus on the highest-risk areas first.

Leading platforms and successful techniques

Modern platforms provide the visibility needed to reduce the attack surface across the entire digital ecosystem:

• UpGuard: Excels in providing continuous visibility and monitoring for the external attack surface and third-party risk. By quantifying the security posture of vendors and suppliers using security ratings, UpGuard helps organizations reduce their supply chain attack surface—a vital step, as third-party connections are frequent initial access points.
• Microsoft Defender for Endpoint: Provides predefined attack surface reduction (ASR) rules that can be configured to block risky software behaviors, such as launching suspicious scripts or untrusted executable files in office applications. These rules serve as an automated layer of defense on your endpoints.
• Network and cloud policy management (e.g., Tufin): Tools focused on network security can provide continuous visibility into firewall rules, helping organizations identify unused, overly permissive, or shadowed rules. Cleaning up these policies across hybrid and cloud environments directly shrinks the network attack surface.

The power of continuous monitoring is its ability to identify and eliminate exposures before they can be exploited. For example, by implementing automated discovery, an organization can quickly identify a forgotten development server with a publicly exposed admin port that has fallen outside the standard scanning regimen. By immediately decommissioning or isolating that single asset, the team successfully prevents a potential compromise that could have cost the company millions in breach costs and downtime.

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