Tezos position paper describes checkpointing (not the disk storage check pointing coming in tezos-node soon) and TAPOS as protection against long range attacks.
Are they implemented somehow in the current eco-system?
I found an effort for the checkpoint:
https://tezosbtc.com/ burns Tezos block hashes into Bitcoin blockchain.
The following video https://www.youtube.com/watch?v=WEjxfpREhzQ&feature=youtu.be explains the details.
