If you are using a stock WordPress installation, take a look at your robots.txt file and it will most probably say something like:
User-agent: *Disallow: /wp-adminDisallow: /wp-includesThe problem with this is that there are many bots which will hit you very hard if you don’t specifically block them. Here is a better robots.txt file:
User-agent: *
Disallow: /wp-content/Disallow: /wp-icludes/Disallow: /trackback/Disallow: /wp-admin/Disallow: /archives/Disallow: /category/Disallow: /tag/*Disallow: /tag/Disallow: /wp-*Disallow: /login/Disallow: /*.js$Disallow: /*.inc$Disallow: /*.css$Disallow: /*.php$
User-agent: AllAllow: /
User-agent: Googlebot-ImageDisallow: /
User-agent: ia_archiverDisallow: /
User-agent: duggmirrorDisallow: /
User-agent: YandexDisallow: /
User-agent: mogetUser-agent: ichiroDisallow: /
User-agent: NaverBotUser-agent: YetiDisallow: /
User-agent: BaiduspiderUser-agent: Baiduspider-videoUser-agent: Baiduspider-imageDisallow: /
User-agent: sogou spiderDisallow: /
User-Agent: SlurpDisallow: /Feel free to fork and create better versions.
Just keep in mind that there are still a lot of other bad/useless bots out there which will consume your resources, but many of them do not respect robots.txt. You will have to block their IPs in your .htaccess (or other similar conf files depending on your server).
I believe the new WordPress has already set now follow tag on some of its component, like wp-admin and wp-login. There is also a WordPress plugin which create robots.txt file blocking unwanted bots.