First of all KSN doesn't works properly, every file i test (infected or not) i get a today first time detected, even those that i'm sure Kaspersky has them a long time ago in their database. Just read the forum and saw that this is a common problem :dodgy:. Second and final, there are ups and downs when it comes to detection. One day you get 100% detection and the next day you can get 80%-90%. So if you already paid for it ,keep it.