Fileless malware is a type of malware that is designed to reside and execute entirely in the memory of a host system, without leaving any trace on the local disk. This can make it more difficult for security tools to detect and remove the malware, as it does not leave any files on the system that can be scanned or deleted.

Fileless malware is typically delivered through a variety of means, such as email attachments, malicious websites, or exploit kits. Once it has been delivered to the host system, it may use a variety of techniques to avoid detection and persist in the memory of the system. This can include modifying system settings, injecting code into legitimate processes, or using fileless malware-specific tools and frameworks.

Fileless malware can be difficult to detect and mitigate, as it does not leave any physical evidence on the system and can often evade traditional security measures that rely on scanning and analyzing the local disk. As a result, it is important for individuals and organizations to take steps to protect themselves against this type of malware, such as by keeping their systems and applications up to date, practicing safe browsing habits, and using security software that is designed to detect and mitigate fileless malware threats.