For the strong player, the challenge is to beat IGOWIN giving it a three-stone handicap. If you can beat it at four stones, you are a strong 4- or 5-dan. To beat it consistently at five stones puts you at the professional level.
The computer program for IGOWIN was developed by David Fotland. His program for 19x19 go is sold under the name The Many Faces of Go. This product is available from Yutopian http://www.yutopian.com