GIANT AntiSpyware was a spyware detection and removal application developed by GIANT Company Software, Inc.

GIANT Company Software, Inc. was acquired by Microsoft Corporation on December 16, 2004. GIANT AntiSpyware is no longer sold and Microsoft stopped releasing spyware definition updates for it in August 2006.

Microsoft's Windows Defender

Windows Defender

Windows Defender, formerly known as Microsoft AntiSpyware, is a software product from Microsoft to prevent, remove, and quarantine spyware in Microsoft Windows...

 (formerly Microsoft AntiSpyware) program is built upon a restructured version of GIANT AntiSpyware.

Sunbelt's Counterspy

Counterspy

CounterSpy is a proprietary spyware removal program for Microsoft Windows software developed by Sunbelt Software.-Features:CounterSpy scans a PC for spyware, examining files on the hard drive, objects in memory, the Windows registry and cookies and it has a capability called DNR that, according to...

was based on GIANT and is still usable this day.
But, the code is completely different now than GIANT.