This article is from last year, but it still holds true. The holidays are crazy with infrastructure attacks. Read my synopsis from OG Consulting - http://www.og-consulting.com/2006/12/22/fighting-the-good-fight-against-...
This year, I am noticing the spammers have gotten really smart. I see emails slipping through the filters, and I almost have to applaud them. "Way to go, bravo." They are simple, short, have maybe one link and have subtle and sometimes relevant subject lines. I got one the other day that had a Thanksgiving theme. Inside was a viagra, abilify or some sort of pharmaceutical spam.
On the server level, I've seen a marked increase in the past couple of weeks. I've taken precautions by: