Actually Giant AntiSpyware was owned two guys who had co-ownership.
One guy sold his assets to Microsoft which became Windows Defender then later Microsoft Security Essentials.
The other guy sold is assets to Sunbelt (now GFI) which became CounterSpy then later VIPRE.
For awhile there wasn't much difference between Windows Defender and CounterSpy then even shared the exact same database signatures for about 2 years before going their separate ways.
Some of Giant AntiSpyware technology is still present in many Microsoft security products and VIPRE.
That was a long time ago when spyware was the major form of malware infections.
Yes it does brings back some memories in in days when malware was much worse.