We used basic neural networks in Chapter 8, Beating CAPTCHAs with Neural Networks with Neural Networks. Research in neural networks is creating some of the most advanced and accurate classification algorithms in many areas. The differences between the concepts introduced in this chapter, versus those introduced in Chapter 8, Beating CAPTCHAs with Neural Networks is around complexity. In this chapter, we look at deep neural networks, those with many hidden layers, and also at more complex layer types for dealing with specific types of information, such as images.

These advances have come on the back of improvements in computational power, allowing us to train larger and more complex networks. However, the advances are much more than simply throwing more computational power at the problem. New algorithms and layer types have drastically improved performance, outside computational power. The cost is that these new classifiers...