is a generic detection for malicious files that are obfuscated using particular techniques to protect them from detection or analysis.
A malicious file is generally encrypted and/or compressed and stored inside another program, which decodes the malicious file and loads it. The malicious program may be injected into a clean process or loaded in a new process of its own. Unlike a "dropper", the malicious executable is never written to disk as a separate file.
There are no obvious symptoms that indicate the presence of this malware on an affected computer.