A detection in the format 'Memscan:[variant]', where [variant] can be 'trojan', 'worm', 'virus' or similar, is a Heuristic Detection of a file or program that behaves in a suspicious or potentially harmful manner.
This Heuristic Detection is triggered when suspicious processes/components are found in the virtual memory after a suspect file was executed and examined in a virtual test system.
About Heuristic Detections
Heuristic analysis (also known as behavioral analysis) is an advanced type of antivirus technology that evaluates any potential threats by examining a suspected program's intended actions and effects on a computer system.
To examine a program's potential behavior, the antivirus program or executes it in a self-contained, "virtual system" environment (also known as emulation). This allows the antivirus program to evaluate how the program's behavior affects the virtual system, without compromising or endangering the user's actual system.
A program that appears to perform suspicious or potentially malicious actions will trigger a Heuristic Detection, such as the one above.
For more information about Heuristic Detections, see the Heuristic description.