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In addition to the above posts, you only have to look at the many posts about avast's Web Shield detecting bad URLs and the OP wanting to know if it is true and, 99.9% of the time, Web Shield is correct.
We only use other URL scanners (unmaskparasites, malwareURL, etc) for a second oppinion to reassure the OP that Web Shield is correct.
With Web Shield active, no other link scanner is needed in the avast arsenal.
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