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Subject: [ISN] Delivering the 12kb Bomb
From: InfoSec News <isn () c4i ! org>
Date: 2004-03-18 8:33:07
Message-ID: Pine.LNX.4.44.0403180232500.11849-100000 () idle ! curiosity ! org
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http://www.theregister.co.uk/content/55/36345.html
By Kelly Martin
SecurityFocus
Posted: 17/03/2004
The average size of email-bourne viruses so far this year has been
well under 20 kilobytes. A young virus writer, sitting in his
underwear in his parent's dark basement, takes a hex editor and
modifies a few bytes of the latest Netsky.M (16.5kb), Beagle.J (12kb)
or Mydoom.G (20kb) mutation, spawns a new virus variant, and then
releases it into the wild. The resulting few thousand compromised
machines, a conservative estimate perhaps, will sit naked as drones or
"bots" on the Internet, waiting patiently for their summons and
commands.
A mere 12 kilobytes of action-packed code is impressive. For a 12
kilobyte Beagle, you get total system compromise, plus a highly
effective spam engine. This short column, in comparison, is about 29kb
of plain text and HTML. A 12 kilobyte binary is thus very small. The
latest code that brings a Microsoft computer to its knees is small
enough that it could be silk-screened onto an extra-large t-shirt: a
walking time bomb, if you will. With today's monolithic software
programs and operating systems, often barely fitting compressed on a
CD-ROM, it's easy to see how small bits of malicious code can slip
under the radar.
David vs. Goliath
I still remember the days, many computer-years ago now, when
BackOrifice and SubSeven Trojans first came out. At just over 100kb,
they were impressive in their day. Back then most people were running
Windows 98, and a small 100kb email attachment could easily slip into
the operating system and wreak havoc without ever being noticed. Today
these are 100kb Trojans are monolithic in comparison to our modern
email-based worm-virus-backdoor-spam-engines that tend to be under
20kb; these old relics are still a useful footnote, however, for
watching the long-term evolution of malicious code.
Speaking of monolithic: Windows XP Home Edition requires approximately
1,572,864 kilobytes (1.5Gbytes) for a typical install, according to
Microsoft. Of course, it's better/faster/easier-to-use than previous
versions, as the advertisements say, and if you believe the literature
too it's also less buggy and significantly more secure. The public
relations spin machine for such a large company is fascinating to me -
Windows has become bloated into millions and millions of lines code,
yet it only takes a mere 12 kilobytes to provide full system
compromise and an annoying spam engine. The divide between David and
Goliath has never been greater.
Consider an analogy on the size of modern malicious code: if Windows
XP were the size of the Empire State Building, then the little barking
Beagle virus - the size of a small dog - can come in through the front
door, lift its leg, deliver its payload, and somehow cause the entire
building to come crumbling down. Or, Beagle can simply hold the door
open automatically, so that a large cement truck can drive in and
deliver its mystery payload to the base of the operating system as
required.
When Size Matters
The latest craze in the virus-worm-spam war has seen computer worms
crawling inside of other computer worms - like watching maggots crawl
on top of each other as they make their way through a tender piece of
meat. Some of the latest worms found in the wild have multi-vector
propagation algorithms and also make use of previous viral infections
by Beagle and Mydoom. So basically you start with 12kb of code,
whereby Beagle slips into your email and under the radar, opens a
backdoor, and then gets automatically disabled and replaced later in
the week by a yet-more malicious and larger piece of worm code -
perhaps new code that tunnels the user's GUI onto the Internet,
provides full remote-control capabilities, records keystrokes and
searches for a user's sensitive data.
Worms are crawling on top of worms, eating out holes in Microsoft's
dominant operating systems like a giant piece of swiss cheese in front
of thousands of tiny, malicious rats. I do not know to what extent
Microsoft's code is scrutinized through an exhaustive security audit,
but two years after Bill Gates' long-heralded announcement the holes
in the cheese are larger than they've ever been.
It is no wonder that dozens of virus variants appear just a week or
two after the first incarnation is released into the wild - fitting a
backdoor and a highly effective SMTP spam engine into a mere twelve
kilobytes of code is not easy, and many young programmers want to
learn how it's done. Microsoft could learn a few things from these
bright, if mis-aligned, people to help them write more efficient code.
Perhaps with more efficient code, Windows XP on a modern AMD Athlon,
Intel Pentium or Celeron with a gig of RAM would actually run more
quickly and be more secure than Windows NT was on an old P-100 with 32
Mb of RAM. Who knows? For now we're stuck with millions and millions
of lines code compiled into a giant operating system that can be wiped
out of existence remotely with nothing but a small 12 kilobyte piece
of code, launched by someone in his underwear on the other side of the
world.
-
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