Distributed denial of service attack is a kind of cyber smack. Though this attack is known by everyone, its severity is increasing day by day. It denies the services of the network or online services by flooding with unwanted data and makes things unavailable. The impact of DDoS is very high, always. Recently, Twitter, Spotify, Amazon, and Paypal were severely affected by this DDoS. This made the services unavailable to their customers. Blockchain is one of the trending technology can be used to find the misbehaving nodes alias bots from the peer to peer networks. Due to lack of interoperability in blockchain, Multichain is proposed in this chapter to detect DDoS attacks along with cross chain technology. It is designed to communicate with multiple networks and the cross chain technology is built to have the flow between the different chains using smart contract. Deep learning models such as CNN and LSTM are trained and tested with CICDDOS2019 dataset and selected LSTM as the best model and installed at Multichain for detecting the malicious activity and blacklisting it immediately.