No, you don’t need my social security number.

Online Threats, Phone, Security


– (phone rings) Hello.
– Hello, I’m calling from American Express. Are you Mr. *****  ******?
– Yes, great that someone finally reacts to my reclamation.
– First I need to verify your identity. What’s your social security number?
– Excuse me but you are calling me on a number that you have in your register, so you can be pretty confident that you are talking to the right person. But I have no way of knowing that you really are from Amex. So YOU tell ME what my social security number is. I know you have it on file.
– (silence) Well, eh … we must identify our customers to be able to serve them by phone. It’s company policy.
– Yes, I know that. But I’m certainly NOT going to give out my number to a stranger who calls and asks for it. I really need some kind of identification from you first.

It went on like that for a while until I proposed a compromise. I told her the first part of my number and she told me the last digits. It all matched and we were able to proceed.

This post is not about American Express, it is about a severe and widespread problem that is visible in this case. The problem is these Social Security Numbers, SSNs, or National Identification Numbers which is a proper global term. They appear in most countries, in many forms and under many names. But they all have two things in common. They were designed to be unique and distinguish persons with the same name. And they are misused for identification.

The practice of using the SSN as proof of identity is really fundamentally flawed. They are used in the same way as a password, knowledge of the “secret” is supposed to prove who you are. The problem is just that the SSN isn’t designed to be secret. If you are a little bit Internet savvy, you know the basic rules for safe passwords. Think of your SSN as a password. It’s assigned once for your whole lifetime and you can’t change it. You are forced to use the same SSN on all services you use. It’s printed on various documents, depending on what country you live in. It’s recorded in numerous registers, and you don’t even know where all those registers are and who’s got access to them. Would you handle the password to your favorite net service this way? Hell, no! Still knowledge of this fundamentally flawed “password” may enable anyone to get credit, order goods, close accounts, etc. in someone else’s name. Scary!

But what can we do about it? Let’s refresh the memory with some practical advice about how to handle your SSN.

  • Do some googling and look for national advice about SSN security in your country. Laws and practices vary and a local source is typically more accurate. But here comes some generic advice.
  • Do not give out your SSN unless you know who he other part is.
  • Verify that the other part has a valid reason to use your SSN before you reveal it.
  • If a business demands your SSN, you can refuse to give it but the business can refuse to serve you. You can either comply or spend your money elsewhere.
  • Some try to phish for SSNs, look out for fraudulent web forms that ask for it.
  • Check what documents you carry in your wallet that have the SSN printed. Avoid carrying those documents daily, if possible, as your wallet may get stolen.
  • Invoices, tax documents etc. may have the SSN printed. Think about how you dispose those papers. If you have a shredder, use it.
  • Needless to say, don’t post the SSN on the net in any context.

This will help a bit, but not cure the fundamental problem. Your SSN is still used and stored so widely that you may be the victim of identity theft even if you do all this.

The problem is really the misuse of SSNs as proof of identity. And the next question is obvious, what should we use instead? Yes, that’s right. There is no common, safe and reliable method for identifying a caller. Some companies have their own methods to improve security. They may require both your SSN and for example a customer number or invoice number. Better, but still not good as those additional numbers aren’t protected very well either. The banks have good systems with sheets of one-time passwords, or similar. These system have been developed with security in mind and are typically reliable enough. They are developed for on-line access but often work for identifying a caller as well.

Banks have good systems, but they are unique for each bank. We would really need national systems, or even better, a global system for reliable identification of persons both on-line and over the phone. More and more of our transactions cross borders and national systems do not help if you are dealing with someone overseas, like in this case. The problem is not technical, public key cryptography and digital signatures could be deployed to achieve this. But agreeing on a reliable global identification standard that won’t become a privacy threat would certainly be a significant political achievement.

So we probably have to live with this flaw for quite a long time. National solutions will no doubt become available in some countries. Estonia is usually quick to utilize new technology and this is no exception, An electronic ID is a good fundament even if reliable identification over the phone still would require some additional technology. But the rest of us just have to acknowledge the risk, keep our non-secret SSNs as secret as possible and hope for the best.

Safe surfing,

Image by DonkeyHotey @ Flickr.


We have the technology today. Are you looking forward to the mark on the forehead or the back of the hand? A QR and scanner can readily identify any single individual! Oh, by the way, this is not a new idea – only the technology is new.

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