AntiSpam letting lots of spam through

In the past 2 weeks or so, my AntiSpam (part of my Norton360) has been letting a LOT of spam through- to the point that sometimes 70% of the emails I receive are spam.  I keep marking all the spam I find, but it keeps showing up!  Very frustrating.

Is there anyway to know if the AntiSpam is really working and doing its job?