Fileless Malware – A Simple Overview (2021)


In 2017, this kind of attack was first noticed. With the gradual technological advancements, several cybercrimes have taken place as well. Although it is difficult to form a fileless malware definition, the idea can be boiled down to a few sentences. Fileless malware refers to one kind of malicious software which aims at infecting computers. The fact that makes it hard for people to detect it and remove is its subtle way of functioning. This fileless malware software does not leave any evidence as in, it does not change anything in the system of the computer and it makes it difficult to understand whether or not the computer has been attacked.

  1. How does fileless malware work?
  2. Types of fileless malware attacks
  3. How can you defend against fileless attacks

1) How does fileless malware work?

Fileless malware works in several ways and there is no particular way that it follows. Attackers have been growing for ages and they know exactly how these computers are protected from malware. They act accordingly and change their strategies from time to time. 

This malware operates in a way similar to the tradition virus. It does not get stored in any file and changes the location of files but it works in memory. It goes to the memory directly which is why fileless malware removal gets difficult at times. Fileless malware attacks fall under the LOC (low observable characteristics) attacks.

One of the fileless malware examples can be how the victim opens one link from one of his spam emails which leads to some obscure page. Then the fileless attack triggers the Microsoft Windows PowerShell and the system eventually gets corrupted. It leaves no signs whatsoever and the computer runs smoothly afterwards. Then the sensitive and private data can be accessed by the attacker who moves to the next device related to the previous one to conduct the same procedure over again.

2) Types of fileless malware attacks

There are several ways by which fileless malware operates and attacks multiple devices. Here are some of the major ways in which it takes place.

  • Phishing and Vishing emails, downloads: Clicking on suspicious random links from your spam emails or downloads can lead to malware attacks. These links look genuine and most of the time leads to a page completely different. The fileless object then gets stored in your PC’s memory that is undetectable. This is how the window registry manipulation works.
  • Through legitimate applications: Many times the attackers target trusted and legitimate applications like Microsoft PowerShell or Window Management Instrumentation and corrupt them from within. Now, upon using these applications, your computer gets hacked which results in data-stealing and hacking. This is called the memory code injection method.
  • Apps that you are already installed: Fileless malware attacks can happen through apps that you have already installed as well. These apps are primarily hijacked and then used by the attackers as a tool to hack your system. 
  • Through legitimate-looking sites: Fileless attackers tend to create legitimate-looking websites online and when you click on any of these, your system is hijacked automatically by the fraudsters. 
  • SamSam Ransomware : When you put in your password for payment or any other purpose, this kind of fileless malware gets activated and the system is eventually hacked.

3) How can you defend against fileless attacks

The major way to prevent these kinds of attacks would be to be aware of such conducts. Not clicking on random and suspicious links, now downloading apps that are not safe, updating browsers regularly, being aware of phishing emails and notifications are some of the major and most effective real-time fileless malware detection techniques. Therefore, the most important aspect is to gain the ability to measure what exactly is happening in your system to cure these kinds of external fileless malware threats.


Thus, the above article explains fileless’ malware, its types, and how you can defend against its attacks.

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