This really wasn't explained clearly, so I'll elaborate.

The Gnutella network is full of a lot of trash, because it's an open network where anyone can distribute any kind of file. As a result, if you insist on using LimeWire, you must definately avoid the filesizes of 851.7kb, 69.4kb, or 0kb. These are the filesizes of commonly distributed viruses on the Gnutella network. In addition, you must also keep in touch with other limewire users in order to be up to date on all the new viruses that have invaded the network.

But yeah, go on and keep using limewire.