When you download any file, always check the size of the file. Software is usually very large, if the file doesnt look right to you then avoid it. You download off other people at your own risk. Gnutella is an open network. The only thing to go by is how large a file is, if it's really small then it is most likely a virus and there's nothing Limewire cant do anything about users sticking viruses in the P2P network.