dstiles - 9:00 pm on Jun 4, 2011 (gmt 0)
Block all 131.107/16. It's not an MS bot block, more of a general hosting range. Many nasties ceom from there, much as they do from Amazon AWS (see WebmasterWorld "Search Engine Spider and User Agent Identification" for details of that!).
bingbot IS msnbot - just the name changes - but I think you can control it in robots.txt by using either word. Neither word would work on the 131.107/16 bots as I doubt very much if they even look at robots.txt.
If you have a lot of scrapes/attacks on your site then I really recommend reading the "Search Engine Spider and User Agent Identification" forum hereabouts.