User-agent: Unknown robot (identified by 'bot' followed by a space or one of the following characters _+:,.;/\-)
Disallow: *

User-agent: Unknown robot (identified by 'robot')
Disallow: *

User-agent: Unknown robot (identified by 'bot' preceded by a space or one of the following characters _+:,.;/\-)
Disallow: *

User-agent: Unknown robot (identified by 'spider')
Disallow: *

User-agent: Unknown robot (identified by 'crawl')
Disallow: *

User-agent: Unknown robot
Disallow: * 

User-agent: Unknown robot (identified by empty user agent string) 
Disallow: *