External IP Addresses to Include in Pentest: Best Practices for Security Testing

Introduction

Penetration testing is crucial for identifying and addressing security vulnerabilities within an organization. External IP address testing is one important part of pentesting, as attackers can target exposed services hosted on them. Therefore, it is important for organizations to perform thorough pentesting of external IP addresses based on risk and approved scope.

Key Points:

• External IP addresses can act as possible entry points into a company’s network, so important in-scope addresses should be tested.
• Excluding important external IP addresses can lead to vulnerabilities that attackers can exploit.
• Pentesting is more effective when experts understand the organization’s network structure or internet-facing systems.

This post explains the best ways to find external IP addresses to include in a pentest. The post also discusses the importance of external IP address testing, how to choose external IP addresses, and the risks of omitting critical addresses. You will also find information on conducting successful pentests of external IP addresses, including scanning, enumeration, and vulnerability assessment techniques.

Why Testing External IP Addresses Is Important

Because they can be entry points into a company’s network, external IP addresses are important for thorough pentesting. Companies can find vulnerabilities that may be exposed to external threats by testing these addresses.

Pentests can be incomplete if they do not include important external IP addresses. This can lead to vulnerabilities being missed. Attackers might be able to exploit vulnerabilities on external IP addresses that were not included in the tests. This can pose a significant security risk and expose data.

Why External Penetration Testing Is Important

Checking your network’s security from the outside helps identify weaknesses in publicly accessible systems. It helps identify whether unauthorized users could access exposed systems or services. External penetration testing is an important step toward better protection.

While cloud security providers and next-generation firewalls can create a sense of safety, security gaps are often caused by human error, misconfigurations, or poor setup. The maturity of your internal security team and the level of stability of your environment will determine the frequency of pentesting.

Compliance and Regulatory Requirements

Depending on the industry and regulatory environment, some businesses must comply with requirements that may include regular third-party penetration testing. These tests are designed to find vulnerabilities that could allow unauthorized access, modification, deletion, or exposure of sensitive data.

Advantages of External Penetration Testing

• Visibility: Understand how an external attacker could target your publicly accessible systems.
• Prioritization: Prioritize vulnerabilities based on their security risks.
• Incident Response Planning: Identify possible attack scenarios and improve response planning.
• Team Readiness: Improve your IT team’s security knowledge through test findings and recommendations.
• Compliance Assurance: Support efforts to meet applicable legal and compliance requirements.

Key Points

• External security testing is important for finding vulnerabilities in public-facing systems.
• Because of human error and misconfigurations, relying only on security tools may not be enough.
• It is best to test regularly, but the frequency can change depending on team maturity and network stability.
• Penetration testing is often required for compliance reasons.

Types of Penetration Testing

Network Penetration Test: A network penetration test assesses exposed network systems, services, and configurations.

As part of external network testing, firewall configurations may be reviewed. This can include reviewing firewall rules, testing exposed services, and validating configurations. Testing may also include routing issues, IPS-related weaknesses, and DNS assessments such as zone transfer checks. As part of this type of testing, approved ports and services on in-scope hosts are scanned and tested. Testing may include common services such as SSH, SQL Server, MySQL, SMTP, FTP, and more. If black-box testing is in scope, it may also include common web portals such as webmail login pages and management interfaces for firewalls, printers, and other systems.

However, external network penetration testing does not usually include deep testing of custom applications owned by your organization. For those, a dedicated web application penetration test is required. Similarly, a basic network penetration test may not cover custom non-web applications or services because they require additional information and scope definition. Wireless penetration testing and social engineering are not included unless separately scoped.

Network penetration testing can be performed from either an internal or external perspective.

Web Application Penetration Testing: Web applications can be complex, so they require detailed testing. For this purpose, web application penetration testing is used, which is different from network penetration testing. The OWASP Testing Guide covers a broader range of web application testing areas than the OWASP Top 10. Testing coverage depends on various factors like the scope of application, access level, testing time, and agreed-upon rules of engagement.

The scope of web application testing depends on application complexity, authentication flows, APIs, business logic, and third-party integrations. The scope is also affected by what is considered a single application, API, or web service.

A web application test may also include related API endpoints if they are included in the agreed scope. This depends on the design, exposure, authentication, and usage of the API by the application.

Web application penetration testing can be performed from either an internal and external perspective.

Wireless Penetration Test: The main goals of wireless penetration testing are to identify weak protocols, rogue access points, weak or default administrator credentials, and weak pre-shared keys. We also check for common wireless risks such as misassociation, deauthentication attacks, and client misconfigurations.

Because testing equipment needs to be close to the wireless network, an on-site or internal engagement is generally needed.

Social Engineering: Social engineering testing may be conducted remotely or in person.

Remote social engineering may include approved spear-phishing simulations and other authorized electronic testing scenarios involving network or security staff. This type of testing requires careful planning, target approval, employee safety considerations, and controlled payload handling.

Physical social engineering may include authorized media drop tests, physical access attempts, impersonation scenarios, and checks of physical security controls. Physical social engineering is usually performed as part of an internal engagement.

Conclusion

Important external IP addresses should be included in a pentest to help identify vulnerabilities and improve security. Organizations need to follow best practices like choosing IP addresses carefully and ensuring proper coverage to protect themselves. Keeping IP lists up to date and adapting to new cyber threats can help security controls remain effective. SafeAeon can provide expert guidance to improve the penetration testing approach and improve network security.