RICHMOND On the one hand, you can find evidence that no one was ever supposed to use a Social Security number for identification. On the other hand, every credit card application we’ve ever seen asks for that very number and won’t issue a charge card without it.

For decades after Social Security was established in the 1930s, the cards included the phrase "not to be used for identification." But no law was passed to enforce that. And the use and misuse of the precious link to retirement income has expanded exponentially ever since.

We’ve all read about the gigantic problems caused when Target’s computer records were hacked. But no one talks about how thousands and thousands of Social Security numbers were released into the atmosphere, an invasion of privacy that might stay alive for a long time.

That number is like fingerprints -- it belongs to just one person. When that person dies, the number dies, too. People go through stages of wanting to protect it, but the commercial and other uses make that almost impossible. Various government agencies use it -- not just the Social Security Administration. It’s the way the Veterans Administration identifies my husband, for instance. "Last four," they ask, and he rattles off the digits that identify him. And Verizon Wireless does the same.

Hackers such as those who spilled Target’s electronic information into the street are dangerous. But other hazards are out there, too. If you don’t fix it, the number that identifies your bank accounts is on your driver’s license. In Massachusetts, you have the right to request a different number -- we did years ago and it’s a good idea.

As for banks, they are another vulnerable point. The Social Security Administration says if someone knows your name and your SSN and is reasonably good at playing a part, he or she may well convince a bank that a passbook or account number is lost and funds will get transferred out.

With some 400,000 cases of identity theft reported every year, everyone needs to figure out where his or her personal loopholes are. The last four digits of an SSN should not be, the experts say, your ATM pin number or your pin for anything else. (Don’t use your birth date, either.) If your bank uses your SSN as a personal identification number for you (PIN), change it. Change it on your frequent flier accounts and on your license.

If your credit card company sends you new cards with a new expiration date, don’t pitch the expired card into the trash. A thief’s eyes light up at the sight of an undamaged credit card, and thieves are as fond of trash as Sesame Street’s Oscar. Cut it into several bits, drop the pieces in different waste baskets and hope they are separated forever.

Those in the know also advise that you get rid of credit cards you rarely use. The fewer you have, the less exposure. The best thing would be if Congress passed a law forbidding companies to ask for Social Security numbers, a bit like shutting the stall door after the horse has galloped off. But it’s really never too late.

It’s much more complex now than when Social Security was born. Between 1937 and 1939, the SSA made a single payment to recipients. The first was Ernest Ackerman, historians say, and he received 17 cents, paid in 1937. He didn’t, of course, have much time to accumulate the "quarters" that establish how much money a retired person gets.

The next historic moment is owned by Ida May Fuller, a Vermonter who was the first to get monthly benefits. She paid in $24.75 in her three years with the program, then lived to be 100 and collected a total of $22,888.92. The bean counters must have hated that.

Ruth Bass is a former Sunday editor of The Eagle. Her website is www.ruthbass.com.