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February 12, 2025

Internal vs External Penetration Testing: What’s the Difference & Which One Do You Need?

Understanding Internal vs. External Penetration Testing: Which One Does Your Business Need?

Ahmed Qaramany

Ahmed Qaramany

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Hey Real talk let’s break down the difference between internal and external penetration testing and why both matter more than ever in today’s cyber threat landscape, and more relentless every single day. From ransomware that locks down hospitals, to phishing emails that trick even tech savvy employees, attackers are always leveling up so your defenses need to do the same.

And here’s the thing: just installing a firewall and antivirus isn’t enough anymore. If you really want to know how secure your business is, you’ve gotta test it like a hacker would. That’s where penetration testing (or “pentesting” if you’re cool with the lingo) comes in it’s like staging a fake cyberattack to see where your systems might crack before the real bad guys get a chance.

But here’s the twist: not all pentests are created equal. You’ve probably heard of internal and external penetration testing. Sounds a little technical? Don’t worry we’re breaking it down in plain English.

So what’s the deal?

Each one tests totally different things. And depending on your setup whether you’re running a SaaS startup, managing a bank’s infrastructure, or just trying to meet compliance you might need one, the other, or both.

Stick around, because by the end of this guide, you’ll know:

Let’s get into it.

Illustration showing the difference between external attacks from hackers and internal threats from within a network.

What Is Internal Penetration Testing?

So, what exactly is internal penetration testing? Well, imagine this: someone’s already inside your network. Maybe a disgruntled employee. Maybe a hacker slipped in through a stolen VPN login. Or maybe malware got installed through a phishing email last week, and now it’s quietly lurking inside.

Internal pentesting is all about testing “what if that happens?” It doesn’t focus on how someone gets in; it assumes they already did. And now, the question becomes: “What can they do next?”

Here’s what internal testing actually looks at:

Basically, internal pentesting mimics a real attacker who already breached the perimeter and is now looking to escalate access, exfiltrate data, or quietly cause chaos from the inside.

Let’s break this down with a reallife scenario:

🔍 Example: A third party contractor gets access to your internal WiFi to do some quick work. What if they decide to poke around a bit? Internal pentesting simulates what that contractor could do and helps you fix any loopholes before someone with bad intentions tries the same thing.

And here’s something people forget: a lot of threats don’t come from the outside. According to several cybersecurity reports, insider threats whether intentional or not are one of the top causes of data breaches. Internal pentesting helps you stay ahead of that, especially in large organizations where access sprawl gets out of control fast.

Why It Matters

Internal pentests aren’t just about spotting technical flaws. They help you answer critical business level questions:

It’s like a stress test for your internal defenses. Because no matter how “secure” your perimeter is once someone’s inside, it’s a whole different ball game.

What is External Penetration Testing?

Let’s say a hacker’s scanning the internet, looking for easy targets.Your company’s website, email server, cloud dashboard if any of them are exposed, that’s where they’ll strike.

External penetration testing is like giving that hacker permission but in a safe and controlled way.

It’s a simulated cyberattack from outside your organization, testing your perimeter for weak points before real attackers find them.

What’s Usually Targeted?

Here’s what external pentesters typically go after:

These are all things that anyone on the internet can try to reach and attackers absolutely do.

Example Scenario

A startup launches a new SaaS platform super sleek, full of features. But they forget to lock down an old admin panel.

A basic scan from an external pentest catches it, something a real attacker could’ve exploited in minutes.

The Real Goal

It’s not just about finding bugs. It’s about answering key questions:

Because once your public-facing systems are exposed… Well, they’re public. And that makes them a prime target.

Side-by-side comparison of internal and external penetration testing scopes and targets

Internal vs External Pentesting: What’s the Real Difference?

Alright, let’s make this easy. Internal and external pentests are both essential but they test completely different scenarios.

Think of it like this:

Here's how they really stack up:

1. Where the Attack Starts (Attack Origin)

2. What’s Being Tested (Focus)

3. The Type of Threat Simulated

4. What You’re Trying to Prevent (Security Goal)

5. Common Methods Used

Real Talk: Why This Matters

External pentests tell you if bad guys can get in. Internal pentests show you how bad it could get if they do.

You need both to truly understand your security posture otherwise, you’re only seeing half the picture.

Calendar showing recommended schedule for internal and external penetration tests

What to Consider When Planning a Pentest

1. Attack Surface (What’s Being Tested?)

2. Scope of Engagement (How Far Does the Test Go?)

3. Attacker’s Perspective (Who Are They Simulating?)

4. Risks Being Tested (What’s the Threat?)

Which Type of Pentesting Does Your Business Need?

Both are important, but which one you prioritize depends on your business needs.


Your pentesting strategy depends on your business needs and security priorities. If you're unsure where to start, go with external pentesting to secure public assets, then add internal pentesting for full security coverage.

Need Help?

At DeepStrike, we specialize in penetration testing to help businesses stay ahead of cyber threats. Want to improve your security? Let’s talk.

📩 Contact us today at deepstrike.io/contact and let’s secure your business together!