My understanding is that among other things, lifelock places a fraud alert on your credit report.
You can do the same if you want on an annual basis. Used to be you had to do it every 90 days but I believe now it works for a year at a time.
When I had my identity used fraudulently I used the police report to get a seven year fraud alert. During that seven year period whenever I needed to use my credit, not only did I have to unfreeze my credit but I had to prove my identity through a phone call. It meant that things that normally would have been fully automated instead had me waiting on the manual follow up process. The fraud alert places a number on your report and instructions to use it to ensure the person asking for credit is really the person in the credit report.
It was an annoyance but not unmanageable. I remember only having to go through the process a handful of times during the 7 years the fraud alert as on my credit reports.
Not sure if Lifelock is worth it.