Global botnets of "pwned" machines exist. Hypothetically, such a botnet could be configured to look a lot like the Bitcoin peer-to-peer network.
It could even have a long (fake) block chain, full of fake timestamps showing years' worth of history where the difficulty just never got very high.
My question is simple: How does the Bitcoin client know it is connected to the "real" Bitcoin P2P network and not to an impostor? That is, what mechanisms does it use to make this identification with confidence?
The more such mechanisms you identify, the better your answer is, in my view. Thanks.