Many people get confused with the importance of vulnerability scanning and penetration testing. It is not possible for vulnerability scanning to replace the penetration testing, and penetration testing alone cannot secure the entire network.
Both these are important in their own ways as they play an important role in cyber risk analysis and are required by standards such as PCI, HIPAA and ISO 27001.
Penetration testing exploits vulnerabilities in your system architecture whereas vulnerability scanning checks for known vulnerabilities and generates a report on risk exposure.
The penetration testing and vulnerability scanning mainly depend on 3 factors namely Scope, Risk and criticality of assets, Cost and time
Penetration testing scope is targeted and a human factor is always involved in it and automated penetration testing is not possible. Tools and extremely experienced persons are required to conduct the testing.
A good penetration tester can craft a script, changes the parameters of an attack and alter the settings of the tools which are used during a test.
Penetration testing can run at the application level or network level or specific to a function, department or a number of assets. Besides one can include the whole infrastructure and all applications which is actually impractical in a real-world due to the cost and time.
You define your scope on various factors based on risk and the importance of an asset. It is not practical to spend huge money on low-risk assets that may take several days to exploit. Testing needs high-skilled knowledge which is why it is a costly procedure.
Additionally, testers often exploit a new vulnerability or discover security flaws which are unknown to normal business processes. These may take longer days liken few days to few weeks. Due to the cost and its large chance of causing outages, penetration testing is normally conducted once a year. All reports are short and to the point.
Vulnerability scanning is the process of identifying potential vulnerabilities in network devices such as firewalls, routers, switches, servers and applications. This is automated process and aims at finding potential and known vulnerabilities on the network level or application level. They are not supposed to exploit the vulnerabilities. Vulnerability scanners solely identifies known vulnerabilities and so are not built to find zero-day exploits.
The scope of vulnerability scanning is business-wide and requires automated tools to manage the high number of assets. T has larger scope than penetration testing. These are usually performed by administrators or a person with good networking knowledge as product-specific knowledge is needed to effectively use the product of vulnerability scans.
Vulnerability scans can be run on any number of assets to ascertain known vulnerabilities. These scans can then be used to eliminate more serious vulnerabilities that affects your resources by using the vulnerability management life cycle.
The cost of a vulnerability scan is less when compared to penetration testing, and it is a detective control as opposed to a preventive measure like penetration testing.
The Center for Internet Security (CIS) Perspective
The Center for Internet Security (CIS) is a good point of reference for examining the basic differences between vulnerability scanning and penetration testing. CIS maintains an actionable, prioritized list of 20 foundational security controls widely accepted as an authoritative guide to cybersecurity best practices.
Both vulnerability scanning and penetration testing can be fed into a cyber risk analysis process and help determine controls best suited for the business, department or practice. In order o reduce the risks they must work together and in order to get the most out of them, it is very important to know the the difference between them.