is there any rule to stop these kind of attacks ?
http://s8.postimg.org/8df9cedvp/Screen_Shot_2014_02_24_at_3_43_04_PM.png
There is no needs to use mod_security to avoid these requests.
Just try to remove links to your site from:
http://pierceyourmind.com/catbook/index.php?do=/blog/11843/ugg-boots-ebay-uk-earnestfoods-ha2hm1r/ and
http://www.pngindians.com/phpBB/viewtopic.php?t=11064&sid=553164eb160cf7aea1816fe807924c50
I think, it will solve the problem.