I believe there are a couple of closed-source clients that could be (or are already) used for that kind of attack:

- BearShare maybe Vinnie has got an evil twin brother or something or he is cloned by some evil corporation
- Shareaza Who are those guys anyway? Judging from their speed of development, they have quite some resources. Shareaza consists of two words 'share' and 'reaza'. If you change the order of the first two letters the second word becomes 'eraza' or 'eraser'. So Shareaza really is the 'share eraser'. I think Shareaza is sponsored by the RIAA to destroy gnutella once it's popular enough.
- Morpheus 2.0 Incompetence might even be a greater danger to the gnutella network than the RIAA
- QTrax Everyone should know by now that it was created to destroy gnutella.