Avast not stopping trojans

[vht]

Since installing Avast almost a year ago, I've gotten infected with 4 trojans and each time Avast notified me immediatly of the infection but it didnt stop it from infecting my computer.  I may not know much about anti virus software, but isn't the point to not only notify me of the trojan, but to also stop it from getting on my computer?

[Vlk]

Were they stopped really immediately? I mean, haven't they been added to the database later, and then an alarm was triggered?

Also, some Trojans infect via buffer overruns (typically while browsing in IE) - and before the advent of WebShield, avast had not chance to stop these before they got activated (simply because all avast on-access scans were based on disk files - but the Trojan infected (exploirted) directly IE...).

BTW which Trojans are we talking about, exactly?

Thanks
Vlk

[vht]

Were they stopped really immediately? I mean, haven't they been added to the database later, and then an alarm was triggered?

The alarm was triggered as soon as i was infected.  As soon as I opened an EXE or jpg image I got the alarm going off.

Also, some Trojans infect via buffer overruns (typically while browsing in IE) - and before the advent of WebShield, avast had not chance to stop these before they got activated (simply because all avast on-access scans were based on disk files - but the Trojan infected (exploirted) directly IE...).

BTW which Trojans are we talking about, exactly?

Thanks
Vlk

Win32:Trojano-246 & 247
JS:exploit-bytverify-7 & 8
JS:gummy
Win32:Trojano-281
Win32:Mhtplo-8

The first 2 I got from an exe file.  I cant remember where I got the 3rd.  The 281 trojan i got from a jpeg image on a webpage.

I also always use firefox.