Because of the increasing security standards inside operating systems and rapid improvements on malware detection technologies today’s malware authors takes advantage of the transparency offered by in-memory execution methods. In-memory execution or fileless execution of a PE file can be defined as executing a compiled PE file inside the memory with manually performing the operations that OS loader supposed to do when executing the PE file normally. In-memory execution of a malware facilitates the obfuscation and anti-emulation techniques. Additionally the malware that is using such methods leaves less footprints on the system since it does not have to possess a file inside the hard drive. Combining in-memory execution methods and multi stage infection models allows malware to infect systems with very small sized loader programs; only purpose of a loader is loading and executing the actual malware code via connecting to a remote system. Using small loader codes are hard to detect by security products because of the purpose and the code fragments of loaders are very common among legitimate applications. Malware that are using this approach can still be detected with scanning the memory and inspecting the behaviors of processes but in terms of security products these operation are harder to implement and costly because of the higher resource usage (Ramilli, 2010^[1]). Read More