What is penetration testing?

Penetration testing, or pentesting, is a form of ethical cyber security assessment that seeks to identify, safely exploit and help to remediate vulnerabilities across computer systems, applications and websites. By utilising the same tools and techniques used by cyber adversaries, pen testing replicates the conditions of a genuine attack.

Commissioning a penetration test enables organisations to reduce security risk and provide assurance into the security of their IT estates, by mitigating weaknesses before they can be maliciously exploited.

Penetration testing stages

The pen testing process can be broken down into five stages.

1. Planning and reconnaissance
The first stage involves:

  • Defining the scope and goals of a test, including the systems to be addressed and the testing methods to be used.
  • Gathering intelligence (e.g., network and domain names, mail server) to better understand how a target works and its potential vulnerabilities.

2. Scanning
The next step is to understand how the target application will respond to various intrusion attempts. This is typically done using:

  • Static analysis – Inspecting an application’s code to estimate the way it behaves while running. These tools can scan the entirety of the code in a single pass.
  • Dynamic analysis – Inspecting an application’s code in a running state. This is a more practical way of scanning, as it provides a real-time view into an application’s performance.

3. Gaining Access
This stage uses web application attacks, such as cross-site scripting, SQL injection and backdoors, to uncover a target’s vulnerabilities. Testers then try and exploit these vulnerabilities, typically by escalating privileges, stealing data, intercepting traffic, etc., to understand the damage they can cause.

4. Maintaining access
The goal of this stage is to see if the vulnerability can be used to achieve a persistent presence in the exploited system— long enough for a bad actor to gain in-depth access. The idea is to imitate advanced persistent threats, which often remain in a system for months in order to steal an organization’s most sensitive data.

5. Analysis
The results of the penetration test are then compiled into a report detailing:

  • Specific vulnerabilities that were exploited
  • Sensitive data that was accessed
  • The amount of time the pen tester was able to remain in the system undetected

This information is analyzed by security personnel to help configure an enterprise’s WAF settings and other application security solutions to patch vulnerabilities and protect against future attacks.

Who performs pen tests?

It’s best to have a pen test performed by someone with little-to-no prior knowledge of how the system is secured because they may be able to expose blind spots missed by the developers who built the system. For this reason, outside contractors are usually brought in to perform the tests. These contractors are often referred to as ‘ethical hackers’ since they are being hired to hack into a system with permission and for the purpose of increasing security.

Many ethical hackers are experienced developers with advanced degrees and a certification for pen testing. On the other hand, some of the best ethical hackers are self-taught. In fact, some are reformed criminal hackers who now use their expertise to help fix security flaws rather than exploit them. The best candidate to carry out a pen test can vary greatly depending on the target company and what type of pen test they want to initiate.

What are the types of pen tests?

  • Open-box pen test – In an open-box test, the hacker will be provided with some information ahead of time regarding the target company’s security info.
  • Closed-box pen test – Also known as a ‘single-blind’ test, this is one where the hacker is given no background information besides the name of the target company.
  • Covert pen test – Also known as a ‘double-blind’ pen test, this is a situation where almost no one in the company is aware that the pen test is happening, including the IT and security professionals who will be responding to the attack. For covert tests, it is especially important for the hacker to have the scope and other details of the test in writing beforehand to avoid any problems with law enforcement.
  • External pen test – In an external test, the ethical hacker goes up against the company’s external-facing technology, such as their website and external network servers. In some cases, the hacker may not even be allowed to enter the company’s building. This can mean conducting the attack from a remote location or carrying out the test from a truck or van parked nearby.
  • Internal pen test – In an internal test, the ethical hacker performs the test from the company’s internal network. This kind of test is useful in determining how much damage a disgruntled employee can cause from behind the company’s firewall.

How is a typical pen test carried out?

Pen tests start with a phase of reconnaissance, during which an ethical hacker spends time gathering data and information that they will use to plan their simulated attack. After that, the focus becomes gaining and maintaining access to the target system, which requires a broad set of tools.

Tools for attack include software designed to produce brute-force attacks or SQL injections. There is also hardware specifically designed for pen testing, such as small inconspicuous boxes that can be plugged into a computer on the network to provide the hacker with remote access to that network. In addition, an ethical hacker may use social engineering techniques to find vulnerabilities. For example, sending phishing emails to company employees, or even disguising themselves as delivery people to gain physical access to the building.

The hacker wraps up the test by covering their tracks; this means removing any embedded hardware and doing everything else they can to avoid detection and leave the target system exactly how they found it.

What happens in the aftermath of a pen test?

After completing a pen test, the ethical hacker will share their findings with the target company’s security team. This information can then be used to implement security upgrades to plug up any vulnerabilities discovered during the test. These upgrades can include rate limiting, new WAF rules, and DDoS mitigation, as well as tighter form validations and sanitization.