put a fraud alert on your credit report.
Anybody can contact any one of the 3 credit bureaus and ask that a fraud alert be placed on his or her credit report. That credit bureau is obligated by law to repeat the request to the other two bureaus. The consumer merely fills out a simple form (example, for Experian:
https://www.experian.com/consumer/cac/InvalidateSession.do?code=SECURITYALERT). No one can take out credit in your name unless you are first contacted to verify that it is you that is doing the requesting. That's basically all it is. It lasts for 90 days. It makes getting credit only slightly more difficult, in that you need to be able to verify the request. Since I have not intended to apply for credit for quite some time, I have been placing fraud alerts on my reports every 90 days for about a year and a half now.
One perk that comes along with it is that you are eligible for a free copy of your credit report from each of the 3 bureaus within a certain amount of time of placing the fraud alert--in addition to the one free one you are able to get each year (annualcreditreport.com is the official site that is entirely free and makes all 3 reports available. "freecreditreport.com" is for Experian only and will cost you money unless you are diligent and cancel your "trial membership" in True Credit within the time period). So that is a savings of about $27 right there, since I believe a credit report from each bureau costs about $9.
Each time I have placed a fraud alert with one bureau, the other 2 followed up by mail within a very short time confirming that an alert had been placed on my report with them.
So what LifeLock does is simply make that request every 90 days for you. It's for supremely lazy people, I guess, or those not sophisticated enough to know about free fraud alerts.
There is also an Extended Fraud Alert and/or Credit Freeze, but my understanding of these is that it makes it very very difficult even for yourself to get credit--so if you are going to be applying for credit sometime a little later, like six months or a year from now (like, say, a mortgage), just get the regular Fraud Alert, which expires after 90 days.
And credit reports are different from "credit scores," which can be obtained from myfico.com --for the "official" credit scores that banks and mortgage lenders use.