Adware:Adware (or spyware) is a small program that is designed to show advertisements (in various form and degrees of intrusiveness) on your computer. It often reports personal information back to its owners. As a result your sense of privacy can be violated.
The MegaUpload toolbar is affiliated with MegaUpload, an Internet file storage website. The MegaUpload toolbar will record certain aspects of your websurfing activity, and is reported to sometimes come bundled with other tracking programs. Although not a serious risk, we recommend removal for those who are concerned with their online privacy.
Technical details (How to remove MegaUpload Toolbar(pop up))