Surge in unclassified threats and decrease in AWStats?

Since 2 days ago (13th) we have seen a sharp rise in Unclassified Threads in our dashboard (Analytics > Threats).

At the same time we saw a sharp decrease in visits in AWStats.
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We host many xml and audio files for our podcasts.

I’m sure the 2 events are linked somehow but I’m a bit of a noob when it comes to these things and I’m at a loss. I’m not even sure if this is the right place to ask but if anybody can maybe point me in the right direction I can take it from there.

Thank you.