Something like http://www.virustotal.com/ http://www.virustotal.com/ allows you to run a file through a zillion scanning engines. If almost none flag it as malw

Something like http://www.virustotal.com/ http://www.virustotal.com/ allows you to run a file through a zillion scanning engines. If almost none flag it as malware, you've either found a new sample or a false positive. You'd hope that they've at least checked such a service.