What is this hacker trying to do?

Question

If you do a search for:

http://www.google.co.uk/search?q=0x57414954464F522044454C4159202730303A30303A313527&hl=en&start=30&sa=N

you will see a lot of

Answer 1

He is testing your server for SQL Injection, specifically this is a robust test that will work even if its Blind SQL Injection. Blind SQL Injection is when an attacker is able to execute SQL however, there isn't a viewable response. If the http request takes at least 15 seconds the attacker will know that he can execute SQL, and that your running MS-SQL. After this attack he will follow it up with a xp_cmpdshell() to infect your server.