Win Defrag is a rogue system optimizer that acts like a legitimate tool. Win Defrag can be installed onto a PC by Trojans or via drive-by downloads. Win Defrag is designed to coerce users into purchasing its non-existent full version in order to remove or fix falsely detected errors. Win Defrag also has the ability to block Windows programs in order to alarm a victim even further. Do not believe the pop-ups or security alerts displayed by Win Defrag and never waste your money purchasing this rogue.