Is the blockchain good for security?

Overstock was one of the first online retailers to adopt Bitcoin in a big way. Now it's become the first major company to issue stock on a trading platform powered by the blockchain.
The blockchain is a distributed file system where participants keep copies of the file and agree on changes by consensus. The file is composed of blocks, where each block includes a cryptographic signature of the previous block, creating an immutable record.
"Blockchain trading is much more secure than the current