Statistical techniques can be used to evaluate the risk that exploits will be successful in a given network. This type of analysis can help decision-makers to better evaluate the cost of mitigating a threat with the damage that an exploit could cause.
Two general approaches used to do this are deterministic and probabilistic analysis.
The deterministic analysis evaluates risk based on what is known about a vulnerability.
It assumes that for an exploit to be successful all prior steps in the exploit process must also be successful.
This type of risk analysis can only describe the worst case. However, many threat actors, although aware of the process to carry out an exploit, may lack the knowledge or expertise to successfully complete each step on the path to a successful exploit.
This can give the cybersecurity analyst an opportunity to detect the exploit and stop it before it proceeds any further.
The probabilistic analysis estimates the potential success of an exploit by estimating the likelihood that if one step in an exploit has successfully been completed that the next step will also be successful.
Probabilistic analysis is especially useful in real-time network security analysis in which numerous variables are at play and a given threat actor can make unknown decisions as an exploit is pursued.
The probabilistic analysis relies on statistical techniques that are designed to estimate the probability that an event will occur based on the likelihood that prior events will occur.
Using this type of analysis, the most likely paths that an exploit will take can be estimated and the attention of security personnel can be focused on preventing or detecting the most likely exploit.
In a deterministic analysis, all of the information to accomplish an exploit is assumed to be known. The characteristics of the exploit, such as the use of specific port numbers, are known either from other instances of the exploit or because standardized ports are in use.
In probabilistic analysis, it is assumed that the port numbers that will be used can only be predicted with some degree of confidence.
In this situation, an exploit that uses dynamic port numbers, for example, cannot be analyzed deterministically. Such exploits have been optimized to avoid detection by firewalls that use static rules.
The two approaches are summarized below.
Deterministic Analysis – For an exploit to be successful, all prior steps in the exploit must also be successful. The cybersecurity analyst knows the steps for a successful exploit.
Probabilistic Analysis – Statistical techniques are used to determine the probability that a successful exploit will occur based on the likelihood that each step in the exploit will succeed.
