Option C is correct because malware that executes solely in memory without leaving a conventional file on disk is characteristic of fileless malware . CHFI v11 includes Malware Analysis: Static and Dynamic , memory analysis , and the use of controlled labs to inspect malware behavior, all of which are especially important when dealing with threats that avoid leaving traditional disk artifacts.
Fileless malware is challenging because many traditional security and forensic techniques rely on file-based indicators such as suspicious executables, hashes, or disk-resident payloads. When the malware lives primarily in memory, investigators must rely more heavily on live response, memory dumps, process analysis, and volatile artifact examination . That makes detection and reconstruction more difficult, especially after the system is shut down.
Option A may describe a separate evasion method, but it does not directly explain the lack of disk artifacts.
Option B concerns propagation, not stealth in memory. Option D could be a later stage in some infections, but the core challenge described here is the absence of a file-based payload. Therefore, the best CHFI-aligned answer is that this is fileless malware , which is harder to detect and analyze because it executes in memory.