One of the pros Webroot brought to the market was 'scan only when files change'. I remember 4-5 years ago, people thought this was crazy. They wanted to scan files (whether changed or not) ...over and over again. Webroot had to explain this methodology exhaustively. Finally, most AVs took this approach.
I might be wrong, but I think Kaspersky had this methodology way before Webroot.
Another misunderstanding.You are correct. Kaspersky has it at least at 6.0, and Bitdefender also had it about 10 years ago. Probably others too..
Webroot from late 2011 onwards is, in fact, Prevx 4.0+ (Webroot entirely rebuilt its technology on Prevx, having acquired the company for that very purpose). When I started using Prevx in 2006, it was already following this approach—and presumably had been for quite a few years before then. So unless I am mistaken, Prevx/Webroot was very much the first.
I see so many misunderstandings about Webroot here that most of the time I don't bother. Plus I don't want to get into polemical arguments where it seems to be a hobby taunting and hounding, with pretty unpleasant language at that, any poster who dares to say anything other than Webroot is total ##!!$$**. Let's just say that's not my cup of tea and I've learnt my lesson... But this one is so blatant, and so elementary to explain, it just had to be said.