Sometimes malware are FUD (on VirusTotal the detection ratio is 0). A really good method is to analyze the malware with tools like ILSpy, PEiD, IDA, etc. To check file behaviour. Obviously if you find suspicious indicators this doesn't mean a file is malicious but ONLY suspicious.The easy way is 1 . test the file at sanbox. 2. check your file to virus total. I do that and I never did any infection on my computer. And realy i play many with virus and cracks