Am 06.06.2011 22:02, schrieb Darren New:

> Again, the on-demand scanner is the worst possible way, efficiency-wise,
> to detect such things. Where "efficient" means "minimal impact to actual
> users." It should be a last resort, not a primary mechanism.

You need an on-demand scanner though, lest a program opens a file that 
wasn't there when you last had a chance to check it.

Plug in a USB stick full of data, and open something from it right away: 
In that scenario, on-demand is the /only/ efficient mechanism. You don't 
want to tell the user, "sorry pal, that file you're trying to open 
happens not to have been scanned yet - and there's still 4236 other 
files scheduled to be scanned before it."

Likewise, you don't want to clog up the system for minutes just because 
someone inserted a USB stick he only reads one file from.


So in the sense of "total computing & I/O time spent for virus 
scanning", on-demand may be the worst - but "felt" system speed is not 
measured in such ways.


Also note that even if a file has been scanned and hasn't changed, the 
virus database may have; so if you don't want to dig through all files 
on the system every time the virus database changes, on-demand scanning 
provides an advantage there as well. (Ideally of course in that case the 
file would only be checked against virus signatures that were installed 
after the file was last checked.)

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