External penetration testing (pentesting) plays a key role in protecting your Internet-facing infrastructure against outside attacks. Conducting external pentests can help you uncover common vulnerabilities threatening your applications and networks, preventing risks like data breaches and helping you harden your security, maintain compliance, and protect your brand’s reputation. Here’s an overview of external pentest essentials, covering what they are, why you need them, how they work, and how to do them effectively.
External pentests are security assessments of your organization’s Internet-facing infrastructure that simulate attacks in order to identify vulnerabilities that outside actors could exploit. An external pentest systematically maps attack surfaces, identifies potential vulnerabilities, and tests weaknesses in order to prioritize risks and recommend remediations. Conducting external pentests helps your organization prevent security incidents, meet compliance obligations, and protect your brand’s reputation with customers and stakeholders.
External pentests simulate attacks from actors outside your network, in contrast to internal pentests, which simulate attacks from actors already inside your network. Pentests analyze attack surfaces in order to identify and mitigate vulnerabilities. Pentesting forms a category within offensive security testing, which seeks to pre-empt attacks by proactively identifying threats. Offensive security testing also includes vulnerability scanning and red teaming.
Pentests differ from vulnerability scanning, a related type of offensive security testing that places more emphasis on automated detection and less on applying findings. Vulnerability scans identify weaknesses by using automated security tools such as static application security testing (SAST), dynamic application security testing (DAST), interactive application security testing (IAST), and Runtime Application Self-Protection (RASP). In contrast, pentests use primarily manual methods to run scenario-driven security assessments, although they typically use vulnerability scans to gather preliminary information about attack surfaces.
Automated vulnerability scans serve to identify and catalog known vulnerabilities, but can produce false positives. Pentests go beyond automated scan findings by providing exploit validation to verify actual vulnerability, placing exploit context in light of real-world risk, and prioritizing risks and mitigations. The two methodologies complement each other rather than competing.
External pentests differ from red teaming, a similar type of offensive security testing that emphasizes realistic attack simulations where defenders are unaware they’re being targeted. In contrast to pentests, which conduct more comprehensive probes of attack surface vulnerabilities, red team tests target vulnerabilities most likely to be exploited by actual attackers. To better simulate attacks, red teams typically don’t provide advance notice to security teams, while pentesters usually do.
External pentests play a critical role in security because Internet-facing attack surfaces form primary targets for adversaries, representing a first line of defense that must be breached to reach internal targets such as user privileges, data files, and app functionality. These valuable assets easily can be exposed to attackers by common vulnerabilities such as server and app misconfigurations, exposed services, and weak authentication procedures.
Regular pentesting is essential to close these defense gaps and prevent bad actors from accessing your network and apps. Without periodic pentests, you can easily miss emerging vulnerabilities stemming from software updates or new attack methods.
External pentests can cover any area of your external attack surface. Typical targets include:
Pentests are scoped based on your organization’s asset types, digital footprint, security needs, and business priorities. For example, pentests for web applications are scoped based on considerations such as number of user roles, number of dynamic pages using unique templates, and number of single-page application routes.
External pentests follow a standard workflow process that parallels the stages of an attack. Testing stages include:
During the course of this process, pentesters simulate real-world attacker behavior by applying standard frameworks that catalog attacker tactics, techniques, and procedures, such as MITRE ATT&CK and the Open Web Application Security Project (OWASP) Top 10.
External pentests help uncover vulnerabilities characteristic of Internet-facing networks and apps. Some of the most common vulnerabilities include:
External pentests help you pinpoint which vulnerabilities represent your biggest risks and prioritize your remediations.
Ideal pentest frequency varies based on compliance requirements, risk, changes in technology and business environments, and budgetary considerations. Standard best practices and compliance frameworks prescribe annual testing as a minimum. However some compliance frameworks also require testing after major technology upgrades, which is a best practice. Testing is also advisable after major technology deployments, cloud migrations, significant changes to exposed assets, or changes to your threat environment.
As a rule of thumb, annual pentesting is only suitable for organizations with minimal risk levels, stable technology infrastructures, managed security providers, or small security budgets. Higher risk, rapid technology changes, or emerging threats may require more frequent schedules on a semi-annual or quarterly basis. Organizations with the greatest needs and sufficient budgets should consider continuous pentesting to intercept ongoing threats as they emerge.
Successful external pentests depending on careful preparation. Important planning steps include:
Careful preparation improves pentesting depth and efficiency by making it easier to work with your pentesting team or provider.
If your organization lacks in-house pentesting expertise, here are some criteria for choosing an external pentesting provider:
A Pentesting as a Service (PTaaS) provider with a diverse talent pool can help you meet this criteria by connecting you with experienced experts and scaling your testing to meet your needs and budget.
External pentesting forms one component of a comprehensive security strategy. They complement internal pentests that secure your assets. Other key elements include cloud security reviews to secure your cloud-based services, scanning solutions to find vulnerabilities, and continuous monitoring to intercept ongoing threats. Together these security components form a layered defense-in-depth strategy, providing mutually reinforcing safeguards so that vulnerabilities missed by one layer get caught by another.
To learn more about pentesting and other security topics, visit the Cobalt learning center.