Hi,
This should just be a short note: Researchers from USC released a paper claiing they have a mechanism to poison files on Gnutella for only the people who don't pay for the file.
Their claims don't work for current clients, because those support TigerTree hashing which verifies every single chunk you download:
Hash tree - Wikipedia, the free encyclopedia
They also claim that they can poison freenet which is simply wrong, because freenet is not Gnutella program but uses its own protocol.
The paper:
http://gridsec.usc.edu/files/publica...pril8-2008.pdf
More informatio about it on slashdot:
Slashdot IT Story | Researchers Outline Targeted Content Poisoning For P2P Data