The evolution of PC Virus

Malware defense systems: a model
Let‘s start by examining how malware detection technologies work using the following model.

Any protection technology can be separated into two components: a technical component and an analytical component. Although these components may not be clearly separate at a module or algorithm level, in terms of function they do differ from each other.

The technical component is a collection of program functions and algorithms that provide data to be analyzed by the analytical component. This data may be file byte code, text strings within a file, a discrete action of a program running within the operating system or a full sequence of such actions.

The analytical component acts as a decision-making system. It consists of an algorithm that analyzes data and then issues a verdict about the data. An antivirus program (or other security software) then acts in accordance with this verdict in line with the program’s security policy: notifying the user, requesting further instructions, placing a file in quarantine, blocking unauthorized program actions, etc.

As an example, let’s use this model to examine classic methods based on signature detection. A system that gets data about the file system, files and file contents acts as the technical component. The analytical component is a simple operation that compares byte sequences. Broadly speaking, the file code is input for the analytical component; the output is a verdict on whether or not that file is malicious.

When using the model above any protection system can be viewed as a complex number - something that connects two separate constituents i.e. the technical and analytical components. Analyzing technologies in this way makes it easy to see how the components relate to one another and their pluses and minuses. In particular, using this model makes it easier to get to the bottom of how certain technologies work. For example, this article will discuss how heuristics as a method for decision-making are simply one type of analytical component, rather than a truly independent technology. And it will consider HIPS (Host Intrusion Prevention System) as just a type of technical component, a way to collect data. These terms do not contradict one another, and they also do not fully characterize the technology that they are used to describe: we can discuss heuristics without specifying exactly what data is undergoing heuristic analysis, and we can talk about an HIPS system without knowing anything about the principles that guide the system in issuing verdicts.

These technologies will be discussed in more detail in their respective sections. Let’s first examine the principles at the heart of any technology used to search for malicious code: technical (methods for gathering data) and analytical (methods for processing the collected data).

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