It's very possibly bots. I have written (all over the place) about this type of bot attack. Unless you're obsessive (like I am) you might not even notice it until it starts to show up in your Analytics.
I have one site that has been hit by this (out of many). The first time around was in February of 2012. There were IP numbers from all over the world (even though this site is targeted only to a single US state) and they all represented as Windows, and some variant of IE (from 6-9) They were all hitting ONLY the home page, and never going deeper, and they typically would come back for multiple visits (huge bounce rate of course, they just pinged in and pinged back out) Obviously they were executing javascript, because they showed up in Google Analytics and StatCounter. Sometimes there would be as many as several hundred simultaneously on the site, and other times just a handful. At first I was worried they were clicking on ads, but they appeared not to be. After two months almost on the dot, it all stopped.
Then on November 12, 2013, the same site started getting hit again. Mostly the same footprints, except that this time, they were spoofing different viewport sizes (some appearing to be mobile) even while still identifying as Windows 7 or Windows XP (NO Windows 8, interestingly) All still identifying as IE. This time, though, they're hitting the home page, and three of the taxonomy pages (but NOT any pages that were created since the 2012 attack) It's still going on right now, and having talked to a few people who experienced the first attack when I did, it seems they're experiencing the second right along with me now.
There's no practical way to ban by IP; there's tens of thousands (if not more) of them. They come from all countries (lots of Brazil, though) including the US.
As far as I can tell, it's mostly harmless, other than being a PITA for analytics. It doesn't seem to be searching for a file, or clicking on any ads, or trying to go any deeper into the site. It may be some kind of PC virus that executing tasks "under the hood" on the infected PC, and going out to sites with whatever IE is installed, but what the payoff is, I sure don't know. It'll be interesting to see if it stops in January or keeps going. The fact that I got hit the same times as a couple of others makes me think that there's some list of sites that we're on.
