The term “Realtime protection” has been overused in recent years and used in a completely wrong sense ever since it was invented.
To make sure to not be misunderstood – yes, even the company I work for has used the term during the hype of the phrase and recently we published a patch to the “Realtime Protector” (included in a legacy product). However, this still doesn’t make the “protector” more realtime. Now, why is that?
None of the Windows systems is a realtime operating system. So how would any software running under these OSs be “realtime” in any way? Easy answer: it won’t. Since most malware is prevalent on the two Windows platforms (Win9x and WinNT), it is fair to claim that this also means that any anti-malware application isn’t “realtime” either.
Now what does it mean? It means that “realtime protection” is formally and technically a wrong term invented and misused by the marketing experts of the companies offering it. The more proper term would be “on-access scan” as this is exactly what these components do. Whenever you touch (or execute) a file the OAS will scan it and offer you a choice of cancelling your action or deny it right away (depending on the settings). Same for registry operations and whatever else can be “realtime-protected”.