Sober.W is a Trojan that sends email messages to all the addresses it finds in certain files on the computer.
From May 23, 2005 on, Sober.W stops sending emails, attempts to download files from several websites and, if successful, it executes those files.
Sober.W does not spread automatically using its own means. It needs an attacking user's intervention in order to reach the affected computer. The means of transmission used include, among others, floppy disks, CD-ROMs, email messages with attached files, Internet downloads, FTP, IRC channels, peer-to-peer (P2P) file sharing networks, etc.