How does an antivirus detect malware?

Before launching into a discussion on how an antivirus detects malware, it’s important to first understand the term itself; malware is an umbrella term for any type of malicious software. Malicious software can cost you time, lead to financial loss, and even cause emotional loss. Under this term, fall many different types of malware such as viruses, trojans, worms, rootkits, ransomware and more, all of which are categorized according to how they work, how they infect a computer, and their intent. 

But how does my computer become infected with malware?

There is no shortage of tricks used by malware authors to get you to download their malicious files.You might receive spam with an attachment that you open and that ends up installing malware on your PC, or you might end up with malware on your Pc via an infected removable drive such as a USB flash drive that you connected to your PC. You can also infect your computer when you download bundled software from third party websites or files shared through peer-to-peer networks.In general, downloading programs utilities, games, updates, demos, etc., from unreliable sources potentially puts your computer at risk. Malware can also infect your computer when you visit compromised URLs or webpages. However, the biggest offender is not having a powerful antivirus program installed on your system.

How antivirus software detects malware

Because there are so many different existing, new, and emerging types of malware, antivirus (AV) programs today must employ a multi-layer approach to detecting malware. The most widely used of these approaches are described below.

Signature-based. Signature-based threat detection is one of the earliest detection methods, but it is still widely used today. This method is similar to the method we use to identify criminals via their fingerprints. With signature-based detection, the AV looks at a virus’ digital code or signature and compares it against a signature database. If the digital code matches a signature in the signature database, it means that malware has been detected. The problem with signature-based detection is its reliance on known signatures to identify malware. This means it can only identify existing threats; it is ineffective in identifying new and unknown threats. 

Heuristic. Heuristic detection examines files for suspicious-looking commands or instructions. Rather than looking at the virus’ signature, it examines samples of core code looking for established methods of virus programming. Detection of malware occurs whenever the AV detects one of these known methods of virus programming. Heuristic-based detection, while effective, also tends to turn up a lot of false positives.

Behavior-based detection. As the name suggests, behavior-based detection searches for unusual actions or behaviors such as an application sending large chunks of data over the network or disabling security controls. Behavior-based detection can determine whether or not anomalous behavior poses a threat and can even detect previously unknown and new malware.

Data mining. Data mining is one of the latest techniques used by AV programs. Data mining attempts to classify a file’s behavior as either malicious or benign by examining and analyzing its features against patterns in large datasets.

Sandbox analysis. The sandbox analysis method moves files to a secured environment, called a sandbox, and activates and analyzes the files there so they don’t expose the rest of the files to potential malware.

The takeaway

Antivirus software is your first and best line of defense against malware, but to be effective the software must rely on several detection methods as no single method can detect all the different types of malware. Only with a multilayer defense can antivirus programs fully detect and protect your data.