Are Anonymized Usernames necessary?

Question

Our security manager insists that we should use anonymized usernames.

E.g. for a user named John Doe his username would be 'g74h19' instead of something like 'jdoe'.

We already have a policy that locks out an account after three invalid logon attempts. So except maybe for making a DOS attack harder I can't see how this would help security - even worse you would no longer be able to see who is who in the logs.

Are there any security recommendations that support anonymized usernames? (link)

Is anybody here using them?

Answer 1

I'm going to approach this from a Windows domain perspective. If I'm an attacker, I don't care what the usernames are. I simply want them. So I'm going to look for a system that doesn't have RestrictAnonymous, or a Windows 2000 system, and I'm going to scan for all the usernames in the domain. Or I'll gain a single valid user account on the domain and then issue said scans. Now I have ALL user accounts to try against.

Oh and I can scan for groups, too. So I'll look for the really nice ones like Domain Admins or Enterprise Admins or groups which look particularly interesting. And I'll see who are the members of the group in question and look to go after them.

So while anonymizing usernames may seem helpful, I don't think they do much to actually increase security. And they make it harder on end users, support staff, and administrators when troubleshooting a particular set of users' problems.

Answer 2

anonymised user names are another example of security by obscurity. By anonymising the username it makes it difficult for a would be attacker to guess it, from say an email address. Exchange for example often uses the users username as part of the email address.

As you stated you have a lockout policy in effect then you already have some method of security in place and so anonymising will make it more likely to hit the limit with a brute force attack. One thing you should consider is, what if the user inadvertently gives away their password? In a case where there usernames are not anonymised, the attacker has the password and is likely to be able to guess the username from their email in under 3 attempts. If the username is anonymised this is much less likely.

So there is some benefit from having them, but it depends whether this limited benefit outweighs the convenience of easy user names. How much security is enough for your organisation?

Answer 3

Security and Usability must constantly be balanced against each other. This would improve security against a brute force or username guessing attack but makes life far more difficult for the users. The user must now remember 2 pieces of (to them) random information to be able to log in and perform their job functions. This is a risk to the business as the users are more likely to both write down their usernames (and if they're writing that down it's a very short leap to writing down their password with it) or forget their username causing a loss of productivity.

I do not believe that it is worth randomizing usernames. These are shown in clear text on the screen so are very vulnerable to shoulder surfing anyway. They will also cause unnecessary grief for the users. Most importantly they encourage the users to practice bad security habits.

Answer 4

They also can be of use in masking data between employees. People writing reports for payroll etc don't see exactly who is making what. Other situations where if management is choosing layoffs and data on employee performance is presented with anonymous usernames can't be accused of picking and choosing. Random things like that.

It makes a bigger difference for large organizations where taking parts of first names and last names will cause a lot of overlap.

Edit: Obscuring usernames also makes it a bit harder to figure out which user accounts you want to bother trying to hack. With a standard scheme everyone will know the CEO/CIO/CFO/Director usernames. Its a lot harder to figure out which employee number they are.

Answer 5

Working for a .EDU this has come up, but not for security reasons. Like many, we base our usernames (still stuck on 8-character limits due to the presence of older Solaris servers in our user's environment) on the real name at time of registration. Since we have between 19,000 and 23,000 active students at any given time this is done by an algorithm, so guessing what a given user's username is from their real name is not that hard. Depending on how you read the regulations (FERPA), this could count as a 'directory service' of the type that they have a right to opt out of.

This is the problem. If a user with a pretty unique name registers, Farheed Zakaria for example, the account generation process will assign them a username. That would be 'zakarif' in this case. Easy to guess. If you consider this a directory and they opt out, then we'd have to change the username. Changing usernames is a tricky process, and isn't automated. When students get married and change their last names, we do not change their username. We have staff that married in the early 90's that still have usernames that include their old last names.

So, goes the thinking, what if at account-creation we assign users with less easy to derive names? At the university I graduated from, the above name would be "zaka0008"; the first four letters of the last name and a numeric for uniqueness. That isn't easy to derive from the given name, yet still contains some identifiers to help users remember it. That would allow us to avoid doing account renames.

We haven't done this yet, since we haven't had a firm ruling of the applicability of FERPA to this situation. But this is a real world example of going to less obvious usernames.

Answer 6

Technically, the username is half of a cipher so using an easily guessable username is the same thing as using an easily guessable passphrase.