Recently, while we were discussing a contract, an industry executive needed me to give an explanation of the difference between a “security audit” and a “penetration test.” The party with whom the executive was negotiating the contract had changed the contractual requirement from the one to the other. Since this might be of interest to others, I’ll provide the explanation here on the blog.
The short explanation is that a “penetration test” is just one small component of a “security audit,” and that the software / service provider was aiming for a much lower bar than we were aiming for on behalf of the executive and her MLS. Following is an explanation of how much lower it is.
A penetration test is an attempt to find weaknesses in the defenses in a computer system’s security. Sometimes the term is used in reference to non-computer security, but typically not. The test usually consists of a combination of automated and manual testing to find specific attacks that will enable the attacker to bypass certain defenses, then working to find additional vulnerabilities that can be found only once those initial defenses are defeated. As a result of this testing, risk can theoretically be assessed and a remediation plan put in place. One can also evaluate how well an organization detects and responds to an attack.
One significant problem with penetration testing is that, if the system being tested has good outer defenses, a penetration test may not find security risks lurking inside of the defenses. It may then present as its finding that risk is low and no action is needed. Then when there is a change to the outer defense that causes a vulnerability (or a vulnerability is discovered in that outer defense) actual attackers will breach all of the inner layers where security has not been well designed. It’s a well-known principle of security design that one designs multiple levels of security (a/k/a “defense in depth”). Penetration testing, on its own, doesn’t reliably measure whether this has been done properly.
For the more technical readers, I will provide an example:
Let’s say a web application has been written with excellent protections against SQL database injection attacks. The penetration testing is run against the application, no SQL injection issues are found, and the system passes with flying colors. But, let’s say the web application had full database server privileges (a “db_owner” role for MS SQL or a DBA or user with too many global privileges on MySQL), and that the database platform service had full system privileges (an “Administrator” role user on Windows or “root” on Linux). Or let’s say that someone didn’t have mySQL’s “Outfile” disabled along with other issues allowing remote file access. Then, one day, a programmer makes a single mistake (that never happens, right?) and all of the poor configuration behind the web application is exposed and a hacker can easily grab database contents and take over the database server or even the whole network. I’ve taken an attack exactly that far – from the login prompt on the outside of an application – during a sanctioned security audit, of course!
The other problem with using a penetration test as the sole way to measure security is that information security is a much broader area of exploration, normally measured during a full security audit. Most of the breaches we’ve had in this industry have been the result of weak policy and procedure or the contracts that reflect those policies, inadequate human resources practices, and physical security issues. Still other technical security issues have resulted from a lack of protection against screen scraping, and yet others from authentication related issues – both items that most penetration testing tools cannot easily uncover. Looking at the security configuration of network equipment, servers and workstation operating systems, platforms, and installed software, mobile devices, antivirus, printer and copier configuration (yes, I really said copiers!), password selection, backup practices and so much more – all of that falls outside the purview of typical penetration testing and is only reliably addressed via a full security audit.
There’s nothing wrong with using a penetration test as a part of a security audit – just don’t mistake the part for the whole.
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