crawldht

The condition you are explaining is actually a very potential attack called sybil attack which is not only a problem with BitTorrent but also with Tor and Bitcoin. A malicious node can easily setup thousands of nodes of himself. So whenever a client asks for peers, the attacker will give him false IP Addresses which are actually the IP Addresses controlled by the attacker. Thus putting that client into Denial of Service. The attacker returns false IP Addresses to every client who comes to fetch list of peers from him. This technique is actually being used by copyright holders who want to slow down the propagation of their copyright data. The efficiency of attack depends upon the number of malicious nodes an attacker signs up. The attacker can also sign up peers so that he can distribute incorrect data and if he happens to be both DHT node and a peer, he can give you torrent metadata of his malicious data and may start distributing it. It is just that in the end you will realize that hash of torrent doesn't match with the infohash.