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.
SysDefender is a malevolent program disguised as a trustworthy anti-spyware application. SysDefender is aggressively advertised on malicious websites that pretend to scan your system for infections and "detect" quite a bunch of it. SysDefender is designed to profit from unsuspecting computer users, since it is advertised to allegedly eliminate all the threats found on your computer. Both SysDefender and the warnings it displays are fake, and should not be trusted. It is strongly recommended to eliminate SysDefender from your computer without any hesitation.
Technical details (How to remove SysDefender(pop up))