[wp-hackers] Limit Login Attempts

Mark Costlow cheeks at swcp.com
Thu Apr 25 01:13:21 UTC 2013

I agree that obscurity isn't a correct approach to true safety.
Sometimes I still find it useful to add some obscurity to slow them
down a little.  Especially if it's easy to do and doesn't burden the
user (i.e. not making the admin username a meaningless string of

In my environment I can control the initial admin username and
initial password.  Unsophisticated users are unlikely to change the
admin username.  They're more likely to change the password, and
soemtimes they do it in a stupid way no matter how hard we try to
keep them from doing it.  Obscuring the username a bit keeps
them from becoming the lowest hanging fruit.

Anyway, in playing with the /?author=N requests, I found that it does
give up the login name even if that user has not authored any posts.
The HTML output contains:

<body class="archive author author-username author-2 custom-font-enabled single-author">

... where "username" is the name of author N.



On Wed, Apr 24, 2013 at 07:07:26PM -0500, Otto wrote:
> On Wed, Apr 24, 2013 at 6:20 PM, Mark Costlow <cheeks at swcp.com> wrote:
> > One of our customer sites had a related problem today.  A brute-force
> > attacker can learn the names of any potential admin users by sending
> > GET requests for /?author=N where N is a user number.
> First, note that users without published posts will not get the
> redirect from the ?author=N requests. Only published authors will. So
> don't publish using admin credentials and this is mitigated.
> On a wider note, however, usernames are not meant to be considered
> private information, and efforts to hide or treat them as private are
> misguided and potentially harmful. I realize that this is
> counter-intuitive, so allow me to explain:
> Let's consider the consequences if usernames were intended to be
> "hidden" information. If the username was considered secret, then the
> total attack-surface for brute forcing a password would increase,
> because now the attacker must learn both the username and the password
> to gain entry. Instinctively, one might think of this as a good thing,
> but you have to factor in the human element as well.
> For years and years and years, the tech community as a whole has tried
> to drive home the point of "choose a good password". At least some
> users have done this, and the point is well received. However, nobody
> has ever really said "choose a hard-to-guess username too". It's not a
> point to be driven home, and it's not intuitive. People tend to use
> simple, alphabetic usernames. So from a security standpoint, treating
> the username as "sensitive info" is problematic.
> More to the point, if we assume the user has a good password to begin
> with, then having an easy to find username doesn't really help the
> attacker any. It's already basically impossible to brute force a
> "good" password. Adding the username to it really is identical to
> increasing the password length, but the problem is that people haven't
> had "choose a hard username" drilled into them. So the username's
> "difficulty" level isn't anywhere near what they're likely to pick for
> a password. A username is, essentially, an extremely poor password,
> given normal human behavior.
> So, treating usernames as secret is a bad idea, because it adds user
> confusion. If they already have a good password, then their username
> doesn't really matter. Asking them to choose a difficult username too
> adds complexity, and people are bad at complexity. If you increase the
> security requirements too much, you end up with the "password on a
> post-it note on the monitor" syndrome. You need to balance good advice
> with how likely people are to actually take that advice.
> Additionally, many modern webservices have eschewed usernames
> entirely, in favor of email addresses. Google, Facebook, etc, these
> have no user names at all. Finding out an email address is easy (you
> can see mine in this email, after all). Does the fact that you know my
> email address make it any easier for you to crack my GMail account?
> I'm guessing not, because I have a good password (and I use 2-factor
> auth, but that's beside the point).
> Yes, the username can sometimes be gotten from an ?author=N method.
> But it can be gotten in other ways too. And, it's irrelevant except in
> a targeted attack, and that sort of attack is doomed to failure if the
> password is a good one to begin with. Encourage good password
> selection, and don't confuse users by encouraging extra and somewhate
> unnecessary security measures as well.
> That's my 2 cents.
> -Otto
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Mark Costlow    | Southwest Cyberport | Fax:   +1-505-232-7975
cheeks at swcp.com | Web:   www.swcp.com | Voice: +1-505-232-7992

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