Kazaa is a popular P2P file sharing client. Originally based upon the proprietary Morpheus P2P client and it's FastTrack network, Kazaa diverged from Morpheus compatibility in early 2002 due to licensing disputes. After the split, Kazaa had become the most popular P2P client in use, and held that title for over two years. However, widespread ISP blockings of the FastTrack network, especially at universities, have forced downloaders to find alternatives to the software. Competing protocols such as Bittorrent and Gnutella have slowly replaced Kazaa, and today's active participants on the FastTrack network are a fraction of what they were four years ago. Additionally, litigation against Kazaa's parent company, Sharman Networks, has contributed to a decline in the software's reputation.
Kazaa is widely believed to contan spyware and, despite Sharman Networks claims to the contrary. The program currently includes advertising technology from Cydoor, which monitors Internet activity and presents relevant advertisements and free downloads to the user. Kazaa also installs the RX Internet Explorer toolbar which intercepts traffic to popular websites and writes in links to competing websites. Older versions of Kazaa included GAIN technology, which sent detailed reports of user's browsing habits to it's developers.
In early 2002 several Kazaa users had become frustrated with the adware included with the program and developed their own FastTrack client by modifying the official Kazaa executable. This modified version, called Kazaa Lite, contains dozens of improvements to the program including new features and reduced limitations, in addition to the removal of the malware. While Kazaa limits the amount of repeat searches performed, Kazaa Lite does not put artificial limits on searches. Kazaa Lite also handles downloads from multiple sources more smoothly than the official program does. As the FastTrack network prioritises clients who share more files, Kazaa Lite 'cheats' and reports the maximum participation level possible. Sharman Networks claims that Kazaa Lite infrings upon their intellectual property, and has taken steps to prevent the use of the software on the FastTrack network.