How do Identity Protection businesses work?

You have probably seen the ads for Lifelock where the CEO gives out his SS#. There is also another called Identity Guard.

My question is how do they know when someone uses your info to apply for credit? Do they have an ‘in’ with Equifax and the other two credit reporting agencies? How do they monitor your account?

Lifelock Dinged $12 Million for Deceptive Business Practices

Clients nationwide are entrusting private financial information to a Tempe anti-identity-theft firm that’s based on a bluff