Spider 
A spider is a program or script that systematically follows URLs on a page gathering information.

Typically search engines use spiders to gather information from web sites to increase there search index.

example search engine spiders:Normally these spiders show on your board as guests. If you want to be able to see search engine spiders that are browsing your forum pages there is a setting under the vBulletin Options section in the AdminCP.

AdminCP > vBulletin Options > Who's Online Options
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