dstiles - 8:39 pm on Jul 31, 2012 (gmt 0)
I have only one "undefined" in this month's (July) security log. It was with an MSIE 8 UA. The hit came from a TalkTalk/Opal (UK) "infrastructure" range that I've blocked for a long time. It runs, amongst other things, a so-called "anti-virus spider" (which hits AFTER the page has been looked at by the visitor! - see recent threads hereabouts).
I'm not saying my hit WAS a spider but it's in the range 126.96.36.199/17 which I've flagged as "includes lots of bots, webmarketing and HuaweiSymantecSpider" and the header was bot-ish.