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Fileless Malware

Fileless malware evades traditional antivirus detection by running entirely in RAM rather than writing to disk, making it harder to discover but also easier to eliminate with a system restart.

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About this video

Traditional malware relies on writing files to a hard drive to establish persistence, ensuring it survives system restarts and continues operating until it is explicitly removed. This approach, however, exposes malware to detection by antivirus and antimalware tools, which routinely scan the file system for known threats. Fileless malware addresses this vulnerability by running entirely in RAM, bypassing the file system altogether and avoiding the scanning mechanisms that most security software depends on. Because RAM is not a common target for real-time malware scanning, this technique significantly reduces the likelihood of detection during an active session. The primary limitation of fileless malware is its lack of persistence. Since RAM is volatile memory, its contents are lost the moment the system is powered down or restarted, taking the malware with it. This makes fileless malware a more effective tool for short-term, stealthy operations but less suited for long-term compromise. Understanding this trade-off between detectability and persistence is essential for grasping how modern attackers approach evasion and why defenders must look beyond file-based scanning to protect systems effectively.

What you'll learn

What's covered

Fileless Malware

Key terms

Malware
Software specifically designed to disrupt, damage, or gain unauthorized access to a system.
Virus
Malicious code that attaches itself to legitimate programs and replicates when executed.
Antivirus
Software designed to detect, prevent, and remove malicious software from a system.
Fileless Malware
Malware that resides in a system's RAM rather than on disk, evading traditional file-based antivirus detection.
Persistence
A MITRE ATT&CK tactic in which an adversary maintains their foothold within a compromised network to survive restarts, credential changes, or other interruptions.

Topics

Fileless Malware Malware Analysis Memory Forensics Antivirus Evasion Cybersecurity Threat Detection

Transcript

Computers nowadays have mechanisms in place to detect malware, so somehow we need to get around those detections. One way that we can do that is through fileless malware.

Typically viruses and malware get installed on a computer on its hard drive. This is important because it creates some sort of persistence. That is, you can restart the computer — or in this case the laptop — but it's still on the computer until something deletes it. The problem with this is that virus scanning and malware scanning, the software that does this, can discover things. They scan the files on the hard drive, and so it becomes more detectable that way.

So one thing that we can do is create malware that is considered fileless, which means that it never actually gets installed on files on the computer. Instead, it runs within RAM. The advantage to this is that a lot of your software isn't actively scanning the RAM for this kind of malware. The disadvantage is that when you restart the computer, then you lose the persistence of it — anything in RAM gets lost, so this virus or this malware will get lost with it. So there's advantages and disadvantages, but this is one thing that we could do to avoid detection.

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