The entire Gnutella network is a game of Russian Roulette - with a 200 shot cartridge, 199 live bullets and one blank. Find another way to get the files that you need. Bittorrent is self-regulating, and is far less prone to fakes, viruses and other garbage. It's not immune, but they're usually caught much faster, and by following a few simple rules (eg: never download a RAR), you can easily avoid problems.

However, if you MUST use Gnutella (with Phex or another client), before you start finding your files, do the following:
1. Perform a search for a long string of random characters. Just hit the keyboard randomly, eg: fd&&Ikjfkjsh2dsihfssk
2. For any results that occur (eg: "[the above] Keygen.exe", "[the above] full album.zip"), ban the host. In Phex, it's in the contextual menu. Use the "unlimited" ban option.
3. Repeat 4 or 5 times

There are file sharers out there that are desperate for you to get a malware infection, to give you porn instead of a real file, or to just *censored* you over. Find them and ban them.

Spend 15 minutes doing this before you start using the program. And every few days, or at least once a week, repeat the process again to catch the *censored*ers.

HOWEVER, the best advice anyone can take when looking at the Gnutella network is AVOID. Learn Bittorrent, find reputable torrent sites (there are plenty), and make the switch from the 90s dark ages into the present day.

As far as Gnutella programs go, Phex seems to be pretty good. It's easy to use, launches and operates cleanly, it's pretty Mac-like, considering it's a cross-platform open-source app. It's just that the technology it sits on (the Gnutella network) is old, insecure, completely abused and riddled with landmines.