News services all over the world reported today (14 April 2000)
that Microsoft programmers had inserted a security-compromising
back door in their FrontPage web server software. Thousands of
websites worldwide may be affected. Representative coverage of this
story can be found at CNET.
Amidst all the nervousness about yet another Windows security
hole, and not a little amusement at the passphrase the Microsoft
programmers chose to activate the back door (“Netscape engineers
are weenies!”) there is one major implication of this story that is
This back door seems to have been present since at least 1996.
That’s four years — *four years* — that nobody but the pranksters
who wrote it has known about that back door. Except, of course, for
any of the unknown crackers and vandals who might have found it out
years ago. All the world’s crackers certainly know about it now
after the worldwide media coverage.
Webmasters all over the world are going to be pulling
all-nighters and tearing their hair out over this one. That is,
webmasters who are unlucky enough to work for bosses who bought
Microsoft. At the over 60% of sites running the open-source Apache
webserver, webmasters will be kicking back and smiling — because
they know that Apache will *never* have a back door like this
Never may sound like a pretty strong claim. But it’s true.
Because back doors (unlike some other kinds of security
bugs) tend to stand out like a sore thumb in source code.
They’re hard to conceal, easy to spot and disable — *if you have
access to the source code*.
It’s the fact that the compromised Microsoft DLL was distributed
in opaque binary form that made it possible for the good guys to
miss this back door for four long years. In the Apache world, every
every one of the tens of thousands of webmasters who uses it has
access to the Apache source code. Many of them actually look at
code difference reports when a new release comes out, as a routine
precaution against bugs of all kinds.
Under all that scrutiny, a back door would be unlikely to escape
detection for even four *days*. Anybody competent enough to try
inserting a back door in Apache knows this in their bones. So it
would be pointless to try, and won’t be tried.
What’s the wider lesson here?
It’s pretty clear. Anybody who trusts their security to
closed-source software is begging to have a back door slipped on to
their system — with or without the knowledge of the people who
shipped the code and theoretically stand behind it. Microsoft HQ is
doubtless sincere when it says this back door wasn’t authorized.
Not that that sincerity will be any help at all to the people who
will have to clean up the mess. Nor will it compensate their bosses
for what could be millions of dollars in expenses and business
If you don’t have any way to know what’s in the bits of your
software, you’re at its mercy. You can’t know its vulnerabilities.
You can’t know what *other people might know about it that you
don’t*. You’re disarmed against your enemies.
Does this mean every single webmaster, every single software
consumer, has to know the source code of the programs they use to
feel secure? Of course not. But open source nevertheless changes
the power equilibrium of security in ways that favor the defence —
it means back doors and bugs have a short, inglorious lifetime,
because it means the guys in white hats can *see* them. And even if
not every white hat is looking, potential black hats know that
plenty of them will be. That changes and restricts the black hats’
Apache has never had an exploit like this, and never will. Nor
will Linux, or the BIND library, or Perl, or any of the other
open-source core software of the global Internet. Open-source
software, subject to constant peer review, evolves and gets more
secure over time. But as more crackers seek and find the
better-hidden flaws in opaque binaries, closed-source software gets
*less* secure over time.
Who knows what back doors may be lurking right now in other
Windows software, only to be publicly acknowledged four years in
the future? Who *can* know? And who in their right mind would be
willing to risk their personal privacy or the operation of their
business on the gamble that this is the *last* back door in
The truth is this: in an environment of escalating
computer-security threats, closed source software is not just
expensive and failure-prone — it’s *irresponsible*. Anyone relying
on it is just asking, *begging* to be cracked. If theory didn’t
tell us that, the steadily rising rate of Windows cracks and
exploits over the last eighteen months would.
Cockcroaches breed in the dark. Crackers thrive on code secrecy.
It’s time to let the sunlight in.
Eric S. Raymond
“…quemadmodum gladius neminem occidit, occidentis telum
[…a sword never kills anybody; it’s a tool in the killer’s
— (Lucius Annaeus) Seneca “the Younger”
(ca. 4 BC-65 AD),