While searching for an explanation of the IEMB3 user agent string - which I can find no useful information about - I ran across this site which at first glance has a very interesting thing going on. The way I got here searching for IEMB3 was kind of odd since the page was just telling me they have no informationa bout IEMB3, however the concept of what they are doing, if legit, can help track down bots and spammers across multiple web sites across the Internet:
How it works is you set up a monitor on your IPs and they tell you if they see any malicious behavior from your IP space. Of course you have to trust these guys to not be doing some monitoring for their own malicious purposes but hopefully someone will look into that. The concept is interesting and by so doing some unsuspecting web site owners may be alerted if their servers are being used by command and control servers to perform dirty work.