Well I do have spam filters on, but of course they only get so much. I find myself deleting spam comments continuously and it can be very aggravating. Just make sure you have any filters available, on. Hopefully, someone, will be able to give you better advice. Good luck!
I have Spam Karma 2 added to my blog, which catches a lot of the blog spam. Typically the kind of spam I get look like trackback links going to blog farms - you know those sites that steal everyone's contents to make a few cents with AdSense?