Twenty years ago, the world of network security was a whole different ballgame. At that time, the big threat was external attackers making their way onto your network and wreaking havoc. As hard as it is to believe now, many businesses and organizations did not even employ firewalls on their networks at that time! The big push among network security professionals then was to ensure that everyone had good firewalls, or “network perimeter” security, in place. This is the time when vulnerability assessment of distributed computer networks became big.

Vulnerability assessment entails examining networks for weaknesses such as exposed services and misconfigurations that could be exploited by attackers to gain access to private information and systems. This type of testing was encouraged by professionals to give businesses and organizations information about the weaknesses that were actually present at the time of testing. At first, vulnerability assessment was usually only conducted against the external network (that part of the network that is visible from outside the business, usually over the Internet).

Most businesses and organizations embraced the need for firewalls and external vulnerability assessments as time progressed. This was not only because doing so made good sense, but because of regulatory requirements penned to meet the requirements of modern laws such as HIPAA, GLBA and SOX. However, many did not see the need for other security studies such as internal vulnerability assessment (VA). Internal VA is like external VA, but looks for weaknesses on the internal network used by employees, partners and service providers that have been granted access and privileges to internal systems and services. The need for internal VA became increasingly important as cybercriminals found ways to worm their way into internal networks or the networks of service providers or partners. As more time passed, and network attacks increased in volume and competency, internal VA became more commonly performed among businesses and organizations.

Unfortunately, despite the increase in vulnerability studies, networks continued to be compromised. One of the reasons for this is the limited nature of vulnerability assessment. When a VA is performed, the assessors usually employ network scanning tools such as Nessus. The outputs of these tools show where vulnerabilities exist on the network, and even provide the consumer with recommendations for closing the security holes that were found. But it doesn’t go so far as to see if these vulnerabilities can actually be exploited by attackers. Also, these tools are limited, and do not show how the network may be vulnerable to combination attacks in which cybercriminals combine various weaknesses (technical, procedural and configurational weaknesses) on the network to foment big compromises. That is where penetration testing comes into play.

Penetration testing is not automated. It requires expert network security personnel to undertake properly. In penetration testing, the assessor employs the results of vulnerability studies and their own expertise to try to actually penetrate network security mechanisms just as a real-world cybercriminal would do. Obviously, the smarter and more knowledgeable the penetration tester is, the more valid the results they obtain. And for the consumer this can be a great boon.

It is true that penetration testing costs more money than performing vulnerability studies alone. What is little appreciated is the money it can save an organization in the long run. Not only can penetration testing uncover those tricky combined attacks mentioned above, it can also reveal which vulnerabilities found during VA are not presently exploitable by attackers to any great effect. This can save organizations from spending inordinate amounts of time and money fixing useless vulnerabilities and allows them to concentrate their resources on those network flaws that present the most actual danger to the organization.