NSA domestic wiretap over-collection

[David Farber <dave () farber net>]

Begin forwarded message:

From: Matt Blaze <mab () crypto com>
Date: April 16, 2009 3:15:24 AM EDT
To: David Farber <dave () farber net>
Subject: NSA domestic wiretap over-collection

For IP, if you'd like.

Today's New York Times is reporting that the NSA has been
over-collecting" purely domestic telephone and e-mail
traffic as part of its warrentless wiretap program:
  http://www.nytimes.com/2009/04/16/us/16nsa.html?hp=&pagewanted=all

According to Eric Lichtblau and James Risen's article,
part of the reason for the unauthorized domestic
surveillance was technological:

> Officials would not discuss details of the over-
> collection problem because it involves classified
> intelligence-gathering techniques. But the issue
> appears focused in part on technical problems in
> the N.S.A.'s inability at times to distinguish
> between communications inside the United States and
> those overseas as it uses its access to American
> telecommunications companies' fiber-optic lines and
> its own spy satellites to intercept millions of calls
> and e-mails.
>
> One official said that led the agency to inadvertently
> "target" groups of Americans and collect their domestic
> communications without proper court authority. Officials
> are still trying to determine how many violations may
> have occurred.

As disturbing as this is, the sad fact is that over-collection
was readily predictable given the way the NSA apparently has
been conducting some of the intercepts. According to court
filings in the EFF's lawsuit against AT&T, the taps for
international traffic are placed not, as we might expect, at
the trans-oceanic cable landings that connect to the US. but
rather inside switching centers that also handle purely domestic
traffic.  Domestic calls are supposed to be excluded from the
data stream sent to the government by specially configured
network filtering devices supplied by the NSA.

This is, to say the least, a precarious way to ensure that
only international traffic is collected, and a curious design
choice given the NSA's exclusively international mandate. My
colleagues and I have been warning of the risks of this
architecture for several years, perhaps most prominently in
this IEEE Security and Privacy article:
   http://www.crypto.com/papers/paa-ieee.pdf
And I raised the point on a panel with former NSA official
Bill Crowell at last year's RSA conference; as I blogged then:
   http://www.crypto.com/blog/rsa_extravaganza/

> There's a tendency to view warrantless wiretaps in strictly
> legal or political terms and to assume that the interception
> technology will correctly implement whatever the policy is
> supposed to be. But the reality isn't so simple. I found myself
> the sole techie on the RSA panel, so my role was largely to to
> point out that this is as much an issue of engineering as it is
> legal oversight. And while we don't know all the details about
> how NSA's wiretaps are being carried out in the US, what we do
> know suggests some disturbing architectural choices that make
> the program especially vulnerable to over-collection and abuse.
> In particular, assuming Mark Klein's AT&T documents are accurate,
> the NSA infrastructure seems much farther inside the US telecom
> infrastructure than would be appropriate for intercepting the
> exclusively international traffic that the government says it
> wants. The taps are apparently in domestic backbone switches
> rather than, say, in cable heads that leave the country, where
> international traffic is most concentrated (and segregated).
> Compounding the inherent risks of this odd design is the fact
> that the equipment that pans for nuggets of international
> communication in the stream of (off-limits) domestic traffic is
> apparently made up entirely of hardware provided and configured
> by the government, rather than the carriers. It's essentially
> equivalent to giving the NSA the keys to the phone company central
> office and hoping that they figure out which wires are the right
> ones to tap.

Architecture matters. As Stanford Law professor Larry Lessig
famously points out, in the electronic world "code is law". Arcane
choices in how technologies are implemented can have at least as
much influence as do congress and the courts. As this episode
demonstrates, any meaningful public debate over surveillance
policy must include acareful and critical examination of how,
exactly, it's done.

More at http://www.crypto.com/blog/nsa_overcollection

-matt






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