These attacks are associated with Indonesian hackers using the e107 ByroeNet scanner. The Casper user agents are hard coded into the "ByroeNet" scanner dated from June 17, 2010.
I found much of this information on multiple searches, but it is best detailed here: [doc.emergingthreats.net...] - as captured in their honeypots and logs.
Bill; I hope that link is acceptable. It is an authority site.