darknet.org.uk — An MIT project has been established to see if you can spoof IP packets or not, and what percentage of ISPs already drop the packets. Here is a good discussion of the project, what it's about, how to intepret the results and so on.
May 5, 2006 View in Crawl 4
n00854180tMay 5, 2006
AFAIK it's not actually difficult to "spoof" an IP packet, the problem arises in that the recipient machine will reply to the fake IP.
shaolintigerMay 5, 2006Submitter
Yeah it's not difficult, but if the ISP null routes the packet because it's spoofed, it becomes pointless. Which is the crux of this project, to see how much of the IP address space allows spoofed packets.