Can vulnerability scanning replace penetration testing?

The pros and cons of penetration resting

Penetration testers, or pentesters for short, are white-hat hackers who attempt to break into a system by uncovering and exploiting vulnerabilities. Penetration tests are the traditional way of testing application and network security, and can be conducted either by internal security professionals or by external security services companies. In practice, they are usually outsourced to external contractors, who can provide dedicated pentesting services and have no prior internal knowledge of the systems and applications.

Penetration tests have many advantages compared to automated vulnerability scanning. By imitating the activities and methods of real-world attackers, pentesting gives the most realistic indication of the current security status. It can also uncover vulnerabilities resulting from business logic flaws that are beyond the reach of automated scanners. Testers can focus on high-value targets and data to indicate where real attacks might come. If agreed with the client, testing can also use social engineering, phishing, and other attack vectors that real cybercriminals have at their disposal. While slow to execute, a penetration test yields no false positives because each vulnerability has been manually confirmed and exploited, so penetration test reports and other test deliverables contain only verified and actionable data.

The downside of penetration testing is that it’s a time-consuming manual process that can’t be automated, accelerated, or readily scaled up. Pentesters use scanning tools and exploit toolkits such as Metasploit to map out assets, locate vulnerabilities, and run exploits. Penetration tests usually focus on high-profile security risks, so they don’t give a full picture of system security. Combined with the high costs of manual testing, this means that penetration tests are only run occasionally, for example as part of an annual red team vs blue team exercise, so they can’t replace regular scanning, especially for applications and systems that change frequently.

How modern vulnerability scanners work

When directly comparing manual penetration testing with automated vulnerability scanning, we are only talking about dynamic application security testing tools (DAST). While static security testing solutions have their place in the development process, they require access to the source code – something that pentesters don’t have. DAST tools are black-box scanners that analyze the running application in a similar way to a penetration tester or a real attacker. Vulnerabilities are found by probing the application and analyzing its responses using heuristics and signature-based testing to detect potentially dangerous behavior.

Compared to manual penetration tests, automated scans are fast and affordable, and can be run as often as necessary, for example before each release. Continuous scanning is also possible to provide automated penetration testing functionality. Because they can be integrated into the development and testing process, vulnerability scanners have the potential to automate security testing at scale. 

On the other hand, automated scanners can only find known vulnerabilities and issues that their heuristic algorithms are programmed to detect. Unlike penetration testers, they can’t find logical errors, combine multiple vulnerabilities to compromise a system, or gain access by exploiting social engineering techniques. Many solutions are also prone to false positives that negate some of the security and performance benefits of automation and integration, especially at scale.

The best of both worlds: Proof-Based Scanning

For large-scale deployments, the biggest advantage of penetration testing over automated scanning is that each reported vulnerability has been manually confirmed and exploited, and there are no false positives. In contrast, many vulnerability scanners return at least some false positives that have to be manually verified to determine if they are real issues. However, there is one vulnerability scanning solution that meets this problem head-on by adding automatic exploitation.

With Invicti’s proprietary Proof-Based Scanning technology, over 94% of direct-impact vulnerabilities are automatically confirmed with 99.98% accuracy. False positives are a major problem in web application security testing, so accurate automatic confirmation can greatly increase the effectiveness of vulnerability testing and bring benefits across the entire software development lifecycle. By automatically and safely exploiting detected vulnerabilities, Invicti combines the efficiency of automated scanning with the confidence of manual penetration testing. After all, if a vulnerability can be exploited, it can’t be a false positive.

How to maximize application security

Considering the high risk of data breaches and the ever-growing importance of data security, running an automated vulnerability scan on a regular basis is a must for any organization that takes its information security seriously. However, even the most accurate vulnerability scanners can’t replace human expertise, so they should be combined with periodic penetration testing that can find vulnerabilities not detected by scanners. Regular vulnerability scanning can help to eliminate known vulnerabilities that account for the majority of cybersecurity incidents, while pentests can reveal more advanced issues to help the organization minimize risk and maintain a good security posture.