How to Engage a Third-Party Pentest Vendor and Strengthen Your Security Posture

Penetration testing, when done periodically, is a highly effective process for discovering vulnerabilities in your technology stack and broader IT infrastructure.This proactive approach helps companies prevent cyber attacks and provides a clear understanding of their current security posture.

It serves as an informed starting point for implementing measures that strengthen defenses and enhance overall security.

This is no longer an option when cyber threats like malware and ransomware continue to be problems that can cripple businesses to bankruptcy in one single incident.

And for this reason, it has increasingly become the responsibility of internal security teams to conduct penetration testing exercises or, at times, to outsource to an external penetration testing service provider for specialized expertise.

Third-party penetration testing services can provide organizations with valuable insights into potential security weaknesses and attack vectors in their IT systems. Engaging penetration testing vendors is often recommended to help identify vulnerabilities and close gaps before attackers can exploit them at scale.

Types of Pentesting Services (Offered by Third-Party Pentest Vendors)

Penetration testing exercises are like simulated attacks, similar to what an attacker does in real-life situations, targeting a server, network, or web application to find security vulnerabilities that could be exploited on a large scale.

There are three main types of pen testing, which differ in the amount of information given to the external security teams before the test:

White box testing: The security team is given full information about the network, including the operating systems, applications, and network layout, to perform a more thorough test, but this can be an expensive option.

• White box testing: The security team is given full information about the network, including the operating systems, applications, and network layout, to perform a more thorough test, but this can be an expensive option.
• Black box testing: In this testing approach, the security team is given no information about the network, and they have to find a way to get inside the network like an attacker would. It is one of the most realistic scenarios, but also the most time-consuming.
• Grey box testing: The security team is given some information about the network or access to non-privileged user accounts, and they have to proceed by finding the system's vulnerabilities from within, just as an attacker would.

The type of pen testing service you choose depends on your needs and budget. If you need the most thorough test possible, white box testing is the best option. But if you are on a tight budget, black box testing is a good choice. And if you need a balance between white box and black box testing, grey box testing might be a more suitable option.

But before selecting a partner, it is very important to consider one key question—how do you distinguish the best provider for you from the rest? Let’s dig a little deeper to learn how to engage a third-party pentest vendor so you can strengthen your security posture.

Choosing Penetration Testing Providers

Software vulnerabilities and misconfigurations are unavoidable, and the worst part is that internal security teams can sometimes unintentionally overlook weaknesses. For this reason, organizations consider a multifaceted approach by partnering with a third-party penetration testing service provider, which is seen as a valuable extension of the team and contributes to an effective security testing process.

This is a critical business decision, as it can directly impact the effectiveness of identifying and addressing vulnerabilities in your organization.

Here are some key factors to consider for selecting the right penetration testing company:

Understanding Your Needs

Understanding your needs will help you address your specific concerns. Say, for instance, which systems are most critical—customer-facing web applications, your internal network, or perhaps your cloud infrastructure.

Identifying your specific concerns and the systems most critical to your business operations will help you understand what you need, which in turn will help you narrow down the field of potential vendors.

It's also crucial to consider your regulatory obligations because overlooking compliance with regulations can lead to potential legal issues, fines, and penalties. Ensure that your chosen partner’s geographic location aligns with your regulatory framework and requirements, so they can provide the most relevant and effective testing services for your organization.

Vendor Experience and Expertise

Drill down deeper into the vendor's experience and expertise. Do they specialize in the areas that align with your needs? Have they worked with companies in your industry or of a similar size? An initial discussion about their specializations will help ensure the vendor is a good fit for your organization’s unique needs.

A good place to start is by reviewing the company’s portfolio and case studies published on their blog to assess their relevant experience. This will provide insight into their leadership and expertise.

Also, check what industry certifications their organization holds, such as GDPR compliance, ISO/IEC 27001, SOC 2, PCI-DSS, and CREST accreditation.

Be sure to look for a provider with qualified professionals who hold respected security certifications, such as AWS Security Specialty, Certified Kubernetes Security Specialist (CKS), Professional Google Cloud Security Engineer, OSCP, CREST CRT, CREST CCT, and CompTIA Security+.

Transparent processes

Depending on your specific needs, your security teams should define the scope of work and identify the areas of your technology stack and infrastructure to be assessed, such as your network, web applications, third-party services, or various devices. And you'll also need to determine the type of project, whether you're looking for a focused penetration test to discover vulnerabilities or a more comprehensive red team exercise designed to train your defense team by simulating an attack.

It's important to clearly understand and outline what the vendor will do during the testing process and how they will report their findings. A partner who is transparent about their methodology, adheres to industry-recognized testing standards (like OWASP, NIST, or PTES), and diligently follows proper reporting practices is more likely to be a valuable collaborator in improving security with external penetration testing.

Benefits of Third-Party Pentest Services

The internal security team is irreplaceable but is often prone to familiarity bias, as it is human nature to become deeply invested in our work, especially in a field as passionate as cybersecurity. But working with a third-party pen testing vendor can help consolidate the efforts of internal teams, ensuring a holistic and strong security posture.

And most organizations are also increasingly shifting their security approach to using PTaaS (Penetration Testing as a Service) platforms for continuous threat detection. It is one of the most economical and productive ways to conduct both automated and manual penetration testing, offering a scalable and flexible solution for managing their increasingly complex digital footprint.
The main benefits of engaging penetration testing vendors include:

• Unbiased assessment: Third-party pentest providers can give an objective assessment of your security posture, as they are not familiar with your internal systems and processes.
• Proactive security: External penetration testing can help overcome bias, which can enable identifying and addressing vulnerabilities faster before attackers do, thus helping you prevent costly data breaches and other security incidents.
• Regulatory compliance: Third-party pentesting providers can also help you navigate the complex regulatory landscape and meet compliance requirements.
• Hands-on expertise: External pentesting vendors usually have more knowledge and advanced expertise in security threats and understanding of the latest attack vectors and vulnerabilities, which can help you strengthen your defense.

The Standard Pentest Process with Third-Party Vendors

Engaging an external penetration testing team is a collaborative effort between your organization and the third-party provider. So, clear communication and defined expectations throughout each phase are crucial for a successful and insightful pentest.

Some of these key phases are:

Scoping

You and the vendor define the scope of the test—which systems, applications, or networks are included, and the types of testing to be performed (e.g., web application, network infrastructure, social engineering). You also discuss the rules of engagement beforehand, which set boundaries such as allowed testing times, communication channels, and any sensitive areas to avoid.

Testing

The external pentesting team gathers information about your targets—publicly available data, network scans, etc. It should be clear what and how they will use automated tools and manual techniques to identify potential weaknesses. Most importantly, the process of how they will attempt to exploit the vulnerabilities, simulating real-world attack scenarios to gauge the potential impact, should be well-defined.

Reporting

The third-party pentest vendor should provide a comprehensive report (weekly, bi-weekly, or monthly) that outlines the discovered vulnerabilities, their severity levels (often using industry-standard metrics like CVSS), and clear remediation advice.

This report will help you prioritize fixes based on risk. Once you’ve patched the vulnerabilities, the vendor may conduct a follow-up test to verify the effectiveness of your fixes.

How Siemba Can Help Strengthen Your Security Posture

To ensure that your external penetration testing program is effective, Siemba's Penetration Testing as a Service (PTaaS) platform can bootstrap your efforts and help your organization proactively identify vulnerabilities and patch any existing weaknesses in your tech stack or infrastructure chain.

Our platform is designed to replicate the actions and methodologies of a skilled security engineer. And it has substantial drill-down capabilities that allow for in-depth analysis with granular reporting features—enabling you to quickly understand the vulnerabilities that are exposed and exploitable.

Simeba's offensive security tea can also help with manual penetration testing activities to strengthen your security posture. We work with many large internet companies, helping them harden the resilience of their IT assets and applications against evolving cyber threats. Get in touch with our engineers to learn more about how you can strengthen security posture with penetration testing.