Snifsteal.A is a Trojan that is a modified version of the Mozilla extension called NumberedLinks 0.9, which is a component of Mozilla used to follow the links included in the websites through the keypad instead of the mouse.
When browsing through Firefox, it obtains the information entered by the users through forms, such as passwords belonging to the instant messaging program ICQ, the FTP server and the email clients IMAP and POP3.
The harvested information is then sent to its author.
Snifsteal.A 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.