Fileless Malware
Malicious software that runs directly in a computer's memory instead of installing files on the hard drive.
Fileless malware↗ is malicious software that operates directly in a computer's memory (RAM) rather than installing a traditional file on the hard drive, often by abusing legitimate, pre-installed tools like PowerShell or Windows Management Instrumentation to carry out its attack. Because there's no obvious malicious file to scan, it can slip past antivirus↗ tools that rely on file signatures.
Fileless attacks are popular with sophisticated attackers precisely because they leave a much smaller forensic footprint and can disappear when a machine restarts. Defending against them requires behavior-based detection that watches for suspicious activity, like a document opening a command shell, rather than simply scanning files for known malware↗ signatures.