For years, cyber security was pretty straightforward—spot the malicious file, quarantine it, and remove it from your computer. If your computer got infected, you only had to run your antivirus software to resolve the issue. But what happens when there’s no file to detect?

Today, fileless malware has become one of the biggest security threats to companies. They are so prevalent that they accounted for 71% of all hacking attempts, according to the Crowdstrike 2023 Global Threat Report.

But what exactly is fileless malware, how does it work, and how can you protect yourself from it? Keep reading to find out.

What is Fileless Malware?

Fileless malware is sophisticated malicious software that differs from traditional malware in that it doesn’t install itself as a program on your computer. Instead, it launches attacks using legitimate applications like Powershell, WMI, and Microsoft Office Macros.

One thing that makes fileless malware dangerous is that it can cripple your system without leaving a trace. It’s memory-based, and since it doesn’t need .exe files to deploy, it can be impossible to remove with a simple antivirus software.

Additionally, fileless malware erases itself once you reboot your computer, making it even harder to detect, remove, and analyze. By the time you realize your system has been compromised, the attacker would have had enough time to steal sensitive data and install backdoors or ransomware.

How Does Fileless Malware Work?

Here is the process a fileless malware follows to infect your device:

The attackers must first gain access to the target machine. This can happen through a phishing email or compromised login credentials.

Instead of downloading a traditional virus, the malware is injected directly into the system memory, often through PowerShell or WMI.

Once deployed, it uses software and other local resources to execute commands. It also establishes a backdoor to give the attacker continuous access to your computer system.

Whether it’s stealing credentials, siphoning sensitive data, or deploying ransomware, the malware completes its goal before erasing itself to avoid detection.

How to Defend Against Fileless Malware

Since AV software cannot protect against fileless attacks, companies must shift to an integrated approach. Here’s what you can do:

Use a VPN for Additional Protection

While a VPN won’t directly stop fileless malware, it can prevent the infection from happening. These tools encrypt user traffic to secure the connection between a user and the internet, preventing man-in-the-middle attacks that can be used to inject fileless malware. Using VPN for PC will also help by blocking access to malicious sites and hiding your IP address from attackers.

Limit PowerShell & WMI Access

If you don’t use these tools, disable or restrict them, as they are among the most common attack vectors for fileless malware. But while this can help, it won’t completely stop fileless malware. An attacker can still use CMD, MTA, VBScript, DCOM, and other tools built into Windows.

Advanced Endpoint Protection

Since legacy solutions like AVs, allowlisting, and sandboxing no longer get the job done, new next-gen endpoint solutions are increasingly becoming available. These focus on behavior analysis rather than just scanning for known threats.

Endpoint protection works by continuously monitoring your machine, incoming and outgoing network traffic, and unusual tasks in PowerShell, WMI, and similar programs.

Enable Multi-Factor Authentication (MFA)

This is one of the most effective ways to protect against password cracking. Even if attackers gain access to your password, MFA can prevent them from gaining access to your machine, escalating privileges, or moving further into your network.

Be Cautious with Email & Links

Many fileless infections begin with phishing emails or malicious websites. Training employees (or yourself) to recognize suspicious messages is a strong first line of defense. Learning how attackers can use social engineering to trick you or others can be the difference between a foiled threat and a costly attack.

This means that using antivirus software is no longer enough to protect your computer or network. As cyber threats evolve, so must your defenses.