I want to block all request from yandex.ru search bot. It is very traffic intensive (2GB/day).
I first blocked one C class IP range, but it seems this bot appear from different IP ranges.

For example: 

spider31.yandex.ru -> 77.88.26.27
spider79.yandex.ru -> 95.108.155.251 etc..

I can put some deny in robots.txt but not sure if it respect this. 
I am thinking of blocking a list of IP ranges.

Can somebody suggest some general solution.