Your Social Security number is a skeleton key in the hands of an identity thief, but it’s not just about money. Those nine digits are used in too many transactions to enumerate, and because of that, there are plenty of opportunities for them to fall into the wrong hands.

Whether we’re talking about tax fraud or more serious kinds of identity theft that could land you on a no-fly or even a most-wanted list–crimes committed by someone pretending to be you are an increasing risk of going about one’s day-to-day business. The dangers are both real and serious. Medical treatments fraudulently procured can exhaust your health insurance or pollute your chart in ways that could be literally fatal. And with more than a billion compromised records “out there,” your Social Security number may already be in play.

Think about all the places that have your number. The financial institutions you do business with use them—from credit card companies to banks to brokerage firms. If you went to college or ever joined a gym, that’s two more places where your SSN can be found. New doctor? They’ll probably want it. Medicare cards – what the heck were they thinking? Your insurance providers have your number, as do the plethora of companies you can’t remember who have it somewhere in an unlocked filing cabinet after a long-forgotten contract that dates back to a time before data-related crimes were prevalent.

It makes no difference if you throw those nine digits around like fans tossing confetti in the Canyon of Heroes, or you’re careful with your personally identifiable information.

The entities and institutions that absolutely require you to ante up with your Social Security number are legion, which is why your SSN is such a valuable commodity. Identity thieves make a living destroying your good name, and the SSN associated with it. Bad debt gets soldered to your SSN and credit history when it’s sold to a collection agency, where it is used to squeeze payment out of debtors who don’t want their credit scores to permanently suffer. It would be an understatement to say that bad debt – legitimate or not – tends to have a limiting effect on your future buying power. The lifetime cost of debt is staggering for those with collection accounts pulling down their credit scores. (You can pull your credit scores for free on Credit.com to see where you stand.)

In addition to being a proxy promissory, your Social Security number is a means of identification—another reason it’s in more hands than you can possibly know. Hospitals and insurers use it to make sure you are who you claim to be (and also to collect on unpaid bills). That means administrative assistants and anyone else with a key or a login—from the cleaning crew to support staff—can potentially put a finger on your file and nab those numbers. Prior to 2011, the Department of Defense made it really easy: the SSN was used to identify enlisted men and women on all identity cards, and the number was emblazoned on dog tags, backpacks and travel gear.

There are, of course, places where you should “just say no” to requests for your SSN, but there are many other places where you simply can’t do that.

SSNs used to be printed on all stripe of documents before the scourge of identity theft. Now where is all that stuff? Did you shred it? Maybe you threw your dog tags into a smelter. You’re still not safe. It pays to be paranoid. Remember the aforementioned confetti raining down on the Canyon of Heroes? In 2012, the Super Bowl champion New York Giants were showered with personally identifiable information that included SSNs and medical information, even details about a 54-year-old woman’s mammogram. How do you know your information wasn’t in that rain of paper?

You have no way of knowing who has your Social Security number, which is why the onus falls on you to be vigilant and practice the 3 Ms: Minimize your exposure, Monitor your credit and financial accounts and Manage the damage when the inevitable occurs and you find yourself a victim of identity theft. The faster you shut down the slime that try to use your SSN to rob you or steal goods and services, the faster they will move on to greener pastures.

The black market for personally identifiable information is huge. There is a booming business for those selling SSNs for the commission of fraud. Some of the larger operations even have customer service representatives. Your mission is to keep those customer service reps busy with calls from would-be fraudsters complaining that your SSN doesn’t work.