Bitcoin's network hashrate surpasses 1 exahash per second (1,000,000,000,000,000,000 hashes per second) around the start of 2016. A milestone in computational security that makes the network effectively impossible to attack through raw computing power. To put it in perspective, 1 EH/s represents more computational work than the combined power of the world's top 500 supercomputers. The hashrate had grown from effectively zero in January 2009 to this staggering figure in just seven years, driven by the evolution from CPU to GPU to ASIC mining.
Bitcoin Wiki: Hash per second