Was discussed a lot in the past… avast has an internal whitelist (cache).
They use 3rd party lists to research. Not directly.
There is a exclusion list into avast settings.
[quote author=pranaygtr link=topic=55865.msg471921#msg471921 date=1266501157]
2. Avast’s Antispyware engine, was created by the ALWIL team or was another company bought out to create the AS engine?
It’s the same as the antivirus engine. The virus (antispyware) definitions were added.