User-agent: * 

Disallow: /*blackhole
Disallow: /?blackhole

User-agent: SemrushBot
Disallow: /

User-agent: dotbot
Disallow: /

User-agent: bingbot
Disallow: /

User-agent: AhrefsBot
Disallow: /

User-agent: MJ12Bot
Disallow: /

User-agent: Krzana bot
Disallow: /
Crawl-delay: 10