What is Mariposa?:
Mariposa is Spanish for butterly. In computer lingo, Mariposa is a botnet created by the Butterfly bot kit. Mariposa is typically spread via instant messaging (usually MSN/Live), peer-to-peer file sharing networks and as an autorun worm
Mariposa steals usernames and passwords and harvests email addresses from infected systems. Mariposa bots may also be directed to launch Distributed Denial of Service (DDoS) attacks.
What is a Botnet?:
A botnet is a collection of compromised (infected) computers under the collective control of remote attackers. The malware on the infected computer is known as a bot, a type of backdoor or remote access trojan (RAT). Bots communicate with botnet command and control (c&c) servers, enabling the remote attacker to update existing infections, push new malware, or instruct the infected computer to carry out specific tasks. In general, the presence of the bot gives the remote attacker the same abilities as the legitimate logged in user.