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71
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57
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+
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<li> Mozilla/5.0 (Windows NT 6.1; rv:19.0) Gecko/20100101 Firefox/19.0
<li> Mozilla/4.0 (compatible; MSIE 8.0; Windows_NT 5.1; Trident/4.0)
<li> Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)
<li> Wget/1.12 (openbsd4.9)
</ul>
The first two UserAgent strings above identify Firefox 19 and
Internet Explorer 8.0, both running on windows NT. The third
Internet Explorer 8.0, both running on Windows NT. The third
example is the spider used by Google to index the internet.
The fourth example is the "wget" utility running on OpenBSD.
Thus the first two UserAgent strings above identify the requestor
as human whereas the second two identify the requestor as a spider.
Note that the UserAgent string is completely under the control
of the requestor and so a malicious spider can forge a UserAgent
string that makes it look like a human. But most spiders truly
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