I've been trying out a service called Tinfoil Security recently. It's basically an automatic hacking system that will try to break into your web site by trying all the tricks that real hackers do. Thousands of them. And if any of the tricks manage to succeed, you get a report so you can plug the hole.
If you run a web site, whether you have your own server or just a shared hosting package, this type of exercise (known as penetration testing) is something that you should definitely try. But if you're wondering whether you can try the test against someone else's site, sadly the answer is no. You'll need to prove that you own the site in question before Tinfoil starts its work.
A subscription to Tinfoil costs from $59 a month, but you get 1 month's free trial so you can easily scan your site a few times before the trial runs out. They also offer a very limited free-forever plan that allows you to check for a specific vulnerability.
Find out more, and sign up, at www.tinfoilsecurity.com and see what you think.