Antivirus software is one of the most important programs, we install in our system. It is designed to protect us from malware, exploits and hackers. However, new threats are emerging everyday and its target is to compromise our system and privacy, and even use infected system to hack another computers. Therefore, an antivirus today is more important than ever. The malware authors are guided mostly by purely financial motives. For example, ransomware aims to encrypt files on a victim's computer to charge the Bitcoin payments for a decryption key.
Most commonly, malware is distributed through websites with malicious software and through email. Usually, the infection requires the user to perform a specific action - for example, opening an email attachment or launching a program downloaded from the Internet. However, it does happen sometimes that the user does not need to do anything to get his or her computer infected with malware. It is enough to visit a web page where you usually read news, which has been recently infected. In such cases, antivirus software turns out to be a very important element - it is precisely the task of antivirus, to protect your privacy and your invaluable files in such cases. But how exactly does antivirus software work? What is a full computer scan and what is a quick scan? How does antivirus detect threats? Why is it constantly updating? This article should answer these questions.
Anti-virus software can use several different scanning methods to detect threats, such as full computer scan, quick scan, or real-time scanner. Let's look at each of them to know how to use them.
A real-time scanner is also known as an on-access scanner. It is likely to be the most useful mechanism offered by antivirus software. It performs scan every time a new program is started, or when you open or download a file, regardless of its type. The antivirus runs the scan before the application interface or the file is presented to the user. The big advantage is that the real-time scanner can also detect security vulnerabilities in running programs. It can, for example, detect in the running program a malicious code that exploits the flash vulnerability. This is why it is recommended not to turn off the real-time scanner. This feature should not be disabled, even if it affects the performance of your computer. Many threats have a big impact on the system performance. Their complete removal can cost us a lot of time and sometimes money.
Most of antivirus software offers a feature called Quick Scan. It scans autostart elements, system memory, and boot sectors for threats. Depending on your anti-virus program, it may also perform scans of places frequently used by malicious software for example for persistence purpose. Often, this mechanism also allows you to scan the system by simply ignoring elements that have not been modified in any way since the last scan. Such a scan uses much less resources and takes considerably less time. This makes it possible to run a scan at any time without significantly reducing the performance of your computer.
Full system scan can take quite a long time. In this process, the antivirus scans all the files on your computer's hard drive, network shares, computer memory, and all media connected to computer, for malware. Today's systems usually accumulate large amounts of data, so it can take a long time to scan. It is recommended to run a full scan of your computer immediately after you have installed antivirus software to ensure that your system is free from malicious software. Another reason why you may want to use a full scan of your computer may be a situation in which you suspect that an infection may not have been detected by a previous version of the virus signature database or checking computer for "dormant" threats.
Scanning mechanisms are not everything. After all, anti-virus must have some way of detecting malware, right? This process uses the database of known threats and heuristics, a mechanism for detecting new or modified versions of malware. Here you will find out what the signature databases really are, and how heuristics work.
The operation of antivirus software largely relies on the use of threat signatures. This is a traditional way of detecting threats in your system. Threat definitions contain the identifiers that are used to determine the type of threat. Every day new threats emerge and, on the basis of their samples, specialists working in antiviral labs creates signatures used for threat detection. Anti-virus software vendors have their own laboratories in which specialists look for new threats and prepare definitions and signatures for them. This is a rather expensive process, as millions of new threats are created each year, and advanced techniques such as reverse engineering are used to analyze them. Using outdated signatures may result in the antivirus being unable to detect new threats. That is why most antivirus solutions update the definition of a threat several times a day.
This method uses a combination of heuristic algorithms and signatures to detect new and modified threats by analyzing similarities. Even if there is no signature for the modified version of the threat, heuristics is able to detect the threat basing on the base version signature and place it in the quarantine. The antivirus uses this definition of the type of threat and can recognize the malicious code in a file with a completely different fingerprint. Another method is to analyze the executable file and checking for performing actions such as modifying or deleting certain files. Standard programs do not try to modify or change important system files, so such actions can be considered potentially dangerous and harmful, so the program will be classified as a threat.
