CRYPTO-GRAM

                  May 15, 2001

               by Bruce Schneier
                Founder and CTO
       Counterpane Internet Security, Inc.
            schneier@counterpane.com
          <http://www.counterpane.com>


A free monthly newsletter providing summaries, analyses, insights, and 
commentaries on computer security and cryptography.

Back issues are available at 
<http://www.counterpane.com/crypto-gram.html>.  To subscribe or 
unsubscribe, see below.


Copyright (c) 2001 by Counterpane Internet Security, Inc.


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In this issue:
      Defense Options: What Military History Can Teach
        Network Security, Part 2
      Crypto-Gram Reprints
      The Futility of Digital Copy Prevention
      News
      Microsoft and the Window of Vulnerability
      Counterpane Internet Security News
      Security Standards
      Safe Personal Computing
      Comments from Readers


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     Defense Options: What Military History
       Can Teach Network Security, Part 2



In Part I of this series, I examined the natural advantages of defense in 
military history.  I concluded that two advantages -- the ability to shift 
forces and knowledge of the terrain -- are underutilized in network 
security.  I concluded that network security based on hidden attack sensors 
and rapid response would be far more effective than firewalls, IDSs, and 
whatever the new new thing next new thing is.

In Part II, I want to look even more broadly at the military's notion of 
defense.  In war, there are three, and only three, types of defense: 
passive defense, active defense, and counterattack.

Passive defenses involve making yourself harder to attack.  Against an air 
assault, for example, this could mean building bunkers or hiding in caves, 
dispersing your forces, or covering yourself in camouflage.  All of these 
defenses have the same goal: reducing the effectiveness of the enemy's 
bombs.  The important thing to note is that while passive defenses make 
attacks less effective, they do nothing to the attackers themselves.

Active defenses are designed to take out the attacker.  Returning to the 
incoming aircraft example, an active attack could be anti-aircraft fire 
that shoots down the attacking aircraft in flight.  This is harder than 
passive defense, but can be much more effective.

Counterattack means turning the tables and attacking the attacker.  Against 
the air assault, it could involve attacking airfields, fuel depots, and 
ammunition storage facilities.  Note that the line between defense and 
offense can blur, as some counterattack targets are less clearly associated 
with a specific attack on a specific target and more geared toward denying 
the attacker the ability to wage war in general.

Warfare has taught us again and again that active defenses and 
counterattacks are far more effective than passive defenses.  Look at the 
Battle of Gettysburg in the American Civil War.  Look at the Battle of the 
Bulge in World War II.  Look at Leyte, Agincourt, and almost any piece of 
military history.  Even in the animal kingdom, teeth and claws are a better 
defense than a hard shell or fast legs.

On the Internet, most people think of computer security in terms of passive 
defenses only.  They believe that if they could only make their systems 
"hard" enough, they'd be safe.  Security vendors reinforce this view, 
providing ever more intricate protection mechanisms for computers and 
networks.  Even the work I've done, pointing out the limitations of 
prevention and extolling the virtues of detection and response, are still 
centered around passive defense.  Part I of this essay was similarly 
limited: the ability to shift forces and knowledge of the terrain are both 
primarily associated with passive defense.

If we're ever going to win the war against computer crime, we're going to 
have to increasingly think more in terms of active defenses, and even 
counterattacks.

We've started to see some of this already.  Intrusion detection systems and 
honeypots provide alarms that can alert defenders of an attack in 
progress.  Managed Security Monitoring services can filter these alarms and 
provide expert response when a network is under attack.  Vigilant, 
adaptive, relentless, expert intelligent network defense is far more 
effective than static security products.  I said all of this in Part I of 
this essay.

But alarm systems, no matter how effective, are still primarily 
passive.  They allow a defender to better survive an attack in progress, 
but they don't put the attacker in danger.  Right now, the only 
counterattack we have is prosecution.  Putting criminals in jail is the 
best deterrent we have, and I am happy to see more of it.  But prosecution 
can only happen after the fact.

One can imagine active defenses and counterattacks, but they are mostly in 
the realm of science fiction.  What if, when an attacker broke into a 
network, his attack program were disabled?  What if he could be sent a 
virus that destroys his computer?  Or, at least, what if some third party 
collected an evidentiary chain that could prove his guilt in court?

There are non-technical considerations as well.  In most countries, active 
defenses can be illegal.  Private citizens can't mine their backyards or 
booby-trap their front doors.  In many countries, it is illegal for them to 
shoot a burglar breaking into their house.  Active defenses are reserved 
for wartime, where there are no rules, or for the police, who have a 
state-sponsored monopoly on violence.

I worry about the vigilante-style cyber-justice that could arise from this 
kind of defense, but it is certainly something we should be thinking 
about.  And it is definitely something that we should be researching.

Passive defense is far from useless, but is not the only form of defense we 
can use.  In many cases, simple active defenses such as monitoring are both 
more effective and more cost effective than adding more passive 
defenses.  "Fortress computer center" was a good model when every company 
had its own unconnected networks.  In today's world, where every network 
must be connected to the global network, it doesn't work as well.  If we 
are ever going to win the war against computer crime, we are going to have 
to emerge from our protective bunkers and actively engage the attacker.


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            Crypto-Gram Reprints



Computer Security: Will we Ever Learn?
<http://www.counterpane.com/crypto-gram-0005.html#ComputerSecurityWillWeEver 
Learn>

Trusted Client Software
<http://www.counterpane.com/crypto-gram-0005.html#TrustedClientSoftware>

The IL*VEYOU Virus (Title bowdlerized to foil automatic e-mail traps.)
<http://www.counterpane.com/crypto-gram-0005.html#ilyvirus>

The Internationalization of Cryptography
<http://www.counterpane.com/crypto-gram-9905.html#international>

The British discovery of public-key cryptography
<http://www.counterpane.com/crypto-gram-9805.html#nonsecret>


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    The Futility of Digital Copy Prevention



Music, videos, books on the Internet!  Freely available to anyone without 
paying!  The entertainment industry sees services like Napster as the death 
of its business, and it's using every technical and legal means possible to 
prevail against them.  They want to implement widespread copy prevention of 
digital files, so that people can view or listen to content on their 
computer but can't copy or distribute it.

Abstractly, it is an impossible task.  All entertainment media on the 
Internet (like everything else on the Internet) is just bits: ones and 
zeros.  Bits are inherently copyable, easily and repeatedly.  If you have a 
digital file -- text, music, video, or whatever -- you can make as many 
copies of that file as you want, do whatever you want with the 
copies.  This is a natural law of the digital world, and makes copying on 
the Internet different from copying Rolex watches or Louis Vuitton luggage.

What the entertainment industry is trying to do is to use technology to 
contradict that natural law.  They want a practical way to make copying 
hard enough to save their existing business.  But they are doomed to fail.

For these purposes, three kinds of people inhabit the Internet: average 
users, hackers, and professional pirates.  Any security measure will work 
against the average users, who are at the mercy of their software.  Hackers 
are more difficult to deter.  Fifteen years of software copy protection has 
taught us that, with enough motivation, any copy protection scheme -- even 
those based on hardware -- can be broken.  The professional pirate is even 
harder to deter; this is someone willing to spend considerable money 
breaking copy protection, cloning manuals and anti-counterfeiting tags, 
even building production plants to mass-produce pirated products.  If he 
can make a profit selling the hacked software or stolen music, he will 
defeat the copy protection.

The entertainment industry knows all of this, and tries to build solutions 
that work against average users and most hackers.  This fails because of a 
second natural law of the digital world: the ability of software to 
encapsulate skill.  A safe that can keep out 99.9% of all burglars works, 
because the safe will rarely encounter a burglar with enough skill.  But a 
copy protection scheme with similar characteristics will not, because that 
one-in-a-thousand hacker can encode his break into software and then 
distribute it.  Then anyone, even an average user, can download the 
software and use it to defeat the copy protection scheme.  This is what 
happened to the DVD industry's Content Scrambling System (CSS).  This is 
how computer games with defeated copy protection get distributed.

The entertainment industry is responding in two ways.  First, it is trying 
to control the users' computers.  CSS is an encryption scheme, and protects 
DVDs by encrypting their contents.  Breaks do not have to target the 
encryption.  Since the software DVD player must decrypt the video stream in 
order to display it, the break attacked the video stream after 
decryption.  This is the Achilles' heel of all content protection schemes 
based on encryption: the display device must contain the decryption key in 
order to work.

The solution is to push the decryption out of the computer and into the 
video monitor and speakers.  To see how this idea helps, think of a 
dedicated entertainment console: a VCR, a Sega game machine, a CD 
player.  The user cannot run software on his CD player.  Hence, a copy 
protection scheme built into the CD player is a lot harder to break.  The 
entertainment industry is trying to turn your computer into an Internet 
Entertainment Console, where they, not you, have control over your hardware 
and software.  The recently announced Copy Protection for Recordable Media 
has this as an end goal.  Unfortunately, this only makes breaking the 
scheme harder, not impossible.

The industry's second response is to enlist the legal system.  Legislation, 
such as the Digital Millennium Copyright Act (DMCA), made it illegal to 
reverse-engineer copy protection schemes.  Programs such as the one that 
broke CSS are illegal to write or distribute under the DMCA.  This is 
failing because of a third natural law of the digital world: the lack of 
political boundaries.  The DMCA is a U.S. law, and does not affect any of 
the hundreds of other countries on the Internet.  And while similar laws 
could be passed in many countries, they would never have the global 
coverage it needs to be successful.

More legal maneuvering is in the works.  The entertainment industry is now 
trying to pin liability on Internet service providers.  The next logical 
step is to require all digital content to be registered, and to make 
recording and playback equipment without embedded copy protection 
illegal.  All in an attempt to do the impossible: to make digital content 
uncopyable.

The end result will be failure.  All digital copy protection schemes can be 
broken, and once they are, the breaks will be distributed...law or no 
law.  Average users will be able to download these tools from Web sites 
that the laws have no jurisdiction over.  Pirated digital content will be 
generally available on the Web.  Everyone will have access.

The industry's only solution is to accept the inevitable.  Unrestricted 
distribution is a natural law of digital content, and those who figure out 
how to leverage that natural law will make money.  There are many ways to 
make money other than charging for a scarce commodity.  Radio and 
television are advertiser funded; there is no attempt to charge people for 
each program they watch.  The BBC is funded by taxation.  Many art projects 
are publicly funded, or funded by patronage.  Stock data is free, but costs 
money if you want it immediately.  Open source software is given away, but 
users pay for manuals and tech support: charging for the relationship.  The 
Grateful Dead became a top-grossing band by allowing people to tape their 
concerts and give away recordings; they charged for performances.  There 
are models based on subscription, government licensing, marketing tie-ins, 
and product placement.

Digital files cannot be made uncopyable, any more than water can be made 
not wet.  The entertainment industry's two-pronged offensive will have 
far-reaching effects -- its enlistment of the legal system erodes fair use 
and necessitates increased surveillance, and its attempt to turn computers 
into an Internet Entertainment Platform destroys the very thing that makes 
computers so useful -- but will fail in its intent.  The Internet is not 
the death of copyright, any more than radio and television were.  It's just 
different.  We need business models that respect the natural laws of the 
digital world instead of fighting them.

Similar sentiment about the death of the PC:
<http://www.theregister.co.uk/content/2/17419.html>


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                     News



"Nihil tam munitum quod non expugnari pecuna possit."  So said Marcus 
Tullius Cicero, a Roman poet, statesman, philosopher and writer who is 
supposed to have lived 106-43 B.C.  Translation:  "No place is so strongly 
fortified that money could not capture it."  (I know this is not news, but 
it's interesting.)

A bug in commercial PGP that allows an attacker to drop files to your disk 
that may then get executed (thanks to Windows .dll loading from current 
working directories).
<http://www.atstake.com/research/advisories/2001/index.html#040901-1>

An excellent article on the dangers of UCITA:
<http://www.itworld.com/Comp/2362/LWD010411vontrol2/index.html>

There is a security flaw in Alcatel DSL modems:
<http://www.pcworld.com/news/article/0,aid,47004,00.asp>
<http://www.zdnet.com/zdnn/stories/news/0,4586,5080984,00.html>
Normally, I wouldn't even bother with this story.  But Alcatel posted a MS 
Word file on their Web site about the problem and fix (which they've since 
removed).  Unfortunately, the file saved deleted changes.  The draft 
document is far more interesting than the real one.  See some of the 
deleted comments here:
<http://morons.org/articles/1/188>

Microsoft responded to my article on the fake certificates in the previous 
Crypto-Gram:
<http://www.microsoft.com/technet/security/verisign.asp>
Greg Guerin has rebutted Microsoft's claims better than I could:
<http://amug.org/~glguerin/opinion/revocation.html>
It turns out that the truth is way more complicated, but no more secure, 
than I had originally thought.

Remember the Egghead.com break last December?  Here the CEO discusses what 
he would and wouldn't do differently if faced with the situation again:
<http://www.retailtech.com/content/coverstories/apr01.shtml>

Anti-sniffing password management software.  I'm not convinced this will 
work, but at least people are thinking about the problem.  Shareware.
<http://32-bitfreeware.virtualave.net/AntiSnoop.zip>

_Body of Secrets_ by James Bamford.  This is his second book about the NSA, 
and it's really good.  I did a review for Salon:
<http://www.salon.com/books/review/2001/04/25/nsa/index.html>
Here's another review from The New York Times:
<http://www.nytimes.com/books/01/04/29/reviews/010429.29findert.html>

CERT is charging companies to get early warnings about threats and 
vulnerabilities.  On the one hand, it's nice to see a little free 
enterprise here.  On the other hand, isn't CERT government-funded?  But 
CERT advisories often appear long after other newsgroups report on 
vulnerabilities, so I don't know how valuable this service really is.
<http://www.msnbc.com/news/561513.asp>
<http://news.excite.com/news/ap/010419/20/computer-security>
<http://news.cnet.com/news/0-1003-200-5665677.html>
<http://www.theregister.co.uk/content/8/18493.html>

Giga has released a report on the Managed Security Services space.  It says 
nice things about Counterpane, but that's almost beside the point.  There 
has been a lot of confusion in the security services space, and the author 
nicely segments the businesses into six categories.  He does a good job 
explaining what the different managed security services are, and which 
companies offer what services.
<http://www.counterpane.com/giga3.pdf>

It's hard to take this particular story seriously, but I have long 
predicted that insurance companies will start differentiating premiums 
based on what kind of networking hardware and software you use:
<http://www.theregister.co.uk/content/8/18324.html>

Impressive investigative work by the FBI.  This is the kind of thing I like 
to see the FBI doing, rather than mucking about with surveillance tools 
like Carnivore.
<http://news.cnet.com/news/0-1007-200-5699762.html?tag=tp_pr>
<http://www.cnn.com/2001/TECH/internet/05/10/fbi.hackers.ap/index.html>
Some disagree with me:
<http://www.zdnet.com/enterprise/stories/main/0,10228,5082126,00.html>

Years ago, ftp was how you shared files between computers.  There are still 
vulnerabilities associated with this service/
<http://securityportal.com/closet/closet20010418.html>

A major legal battle is looming, as the RIAA tries to suppress Princeton 
security research into its digital watermarks, citing secrecy provisions of 
the DMCA:
<http://www.zdnet.com/zdnn/stories/news/0,4586,5081595,00.html>
A preliminary version of the actual paper, and assorted correspondence:
<http://cryptome.org/sdmi-attack.htm>
The site reported over 50,000 visits to the paper within 24 hours of its 
posting.
The RIAA changes its tune:
<http://riaa.com/PR_story.cfm?id=407>

Don't forget mundane security risks.  The British Ministry of Defense has 
lost 205 laptops in the past four years.
<http://www.wired.com/news/politics/0,1283,43088,00.html>

An e-mail was recently sent to Amazon associates, inviting them to visit a 
non-Amazon Web site and complete a questionnaire.  The e-mail purported to 
come from associates@amazon.com, but was actually sent from an entirely 
different domain <jami@interpoll.net>.  When I asked Amazon whether they 
were being spoofed, they told me the survey was legitimate.  Are they 
trying to train their customers to respond to unverified impersonations?

Argus boasted that their secure operating system couldn't be hacked, and 
sponsored a $50K contest.  It was hacked.  The story of how it happened has 
a moral for everyone: security is only as strong as the weakest link, and 
if you're not monitoring your security in real time you need to constantly 
make sure all the links are strong.
<http://www.zdnet.com/enterprise/stories/main/0,10228,2713689,00.html>
Someone else plans on a $1M hacking contest.
<http://www.theregister.co.uk/content/8/18644.html>

Gene Spafford makes much the same points I do about the future of computer 
security: it's going to get worse, not better.
<http://www.cerias.purdue.edu/homes/spaf/ncssa.html>

There have been zillions of articles on this "May Day 
Cyberwar."  Supposedly, the Chinese are attacking the U.S. in retaliation 
for our lousy foreign relations policies.
<http://www.zdnet.com/enterprise/stories/main/0,10228,2714179,00.html>
I believe this is nothing but hacker fantasy and media hype.  I don't see 
hackers with political motivations taking up arms; I see hackers with no 
motivations donning a cloak of politics to justify their actions.  I also 
see the media turning this into a much bigger deal than reality.
<http://www.msnbc.com/news/568036.asp?cp1=1>
<http://www.thestandard.com/article/0,1902,24202,00.html>
<http://www.wired.com/news/politics/0,1283,43520,00.html>

People are the weakest link in security:
<http://news.cnet.com/news/0-1003-200-5798589.html?tag=mn_hd>

U.S. "national security" surveillance is on the rise:
<http://www.securityfocus.com/news/201>

Cyber-thriller screenplay:
<http://www.theatlantic.com/issues/2001/05/frazier.htm>

Comments on NIST's AES FIPS are due by May 29th.  This isn't the time to 
suggest alternate algorithms, but it is time to comment on the details of 
the standard.
<http://csrc.nist.gov/encryption/aes/>

The Dutch government is forcing trusted third parties to use key escrow.
<http://www.telepolis.de/english/inhalt/te/7571/1.html>

Another semantic attack.  A fake BBC Web page was circulating (without the 
caveat at the top), and the British newspapers fell for it.
<http://europe.thestandard.com/article/display/0,1151,16490,00.html>
The fake Web page (with a disclaimer on the top):
<http://news.bbc.co.uk!articles@3276960428/hi/english/uk/newsid/123456.htm>


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       Microsoft and the Window of Vulnerability



In many of my speeches, I talk about a "Window of Vulnerability."  When a 
security vulnerability exists in a product and no one knows about it, there 
is very little danger.  But this state of security is fragile.  As soon as 
someone discovers the vulnerability, the danger increases.  If we're lucky, 
the discoverer is a good guy who does not exploit the vulnerability for 
personal gain.  Eventually word of the vulnerability gets out, and the 
danger increases.

This sounds just like the real world, but cyberspace has a crucial 
difference.  If I knew how to break into a certain kind of ATM, or hot-wire 
a certain make of car, or pick a certain model of lock, I could teach 
someone.  The person I taught would then know how, and he could teach 
others.  But it's a skill, and skills take time to teach.  Cyberspace is 
different because skill can be encapsulated into software.  If I knew how 
to break into Microsoft's IIS 5.0, I could turn my knowledge into an 
exploit and distribute it on the net.  Then, hundreds of thousands of 
"script kiddies" -- with no skill whatsoever -- could use my exploit to 
break into IIS 5.0.  The propagation characteristics of virtual 
vulnerabilities are very different than physical vulnerabilities.

We're seeing this happen right now with an IIS 5.0 vulnerability.  It was 
discovered by a company called eEye Digital Security, which was nice enough 
to warn Microsoft and give them time to create a patch.  Then, Microsoft 
and eEye announced both the vulnerability and the availability of a 
patch.  A few days later, someone wrote an exploit.  As the exploit made 
its way through the hacker community, and continues to do so, more and more 
IIS installations are being broken into.

The press regularly writes the story like this.  First, vulnerability 
discovered and we're all in danger.  Then, vulnerability patched and we're 
all safe again.  What they forget is that patches don't work unless they're 
installed.  And more and more often, people don't install patches.  I 
predict that years from now, Web sites will still be broken into because of 
this vulnerability.

So here's the million-dollar question:  Is eEye Digital Security part of 
the solution, or is it part of the problem?  eEye's own legal disclaimer 
implies that even they're not sure: "In no event shall the author be liable 
for any damages whatsoever arising out of or in connection with the use or 
spread of this information."

Microsoft IIS vulnerability:
<http://www.msnbc.com/news/567192.asp>
<http://www.cert.org/advisories/CA-2001-10.html>
eEye Digital Security's announcement:
<http://www.eeye.com/html/Research/Advisories/AD20010501.html>
Microsoft security advisory and patch information:
<http://www.microsoft.com/technet/security/bulletin/MS01-023.asp>
Exploit published:
<http://www.theregister.co.uk/content/4/18734.html>
<http://www.msnbc.com/news/568503.asp?0nm=T23F>
<http://www.infoworld.com/articles/hn/xml/01/05/03/010503hnattacktool.xml>

Schneier's essay "Closing the The Window of Exposure":
<http://www.counterpane.com/window.html>
The fallacy of installing patches:
<http://www.counterpane.com/crypto-gram-0103.html#1>


** *** ***** ******* *********** *************

       Counterpane Internet Security News



There have been an enormous number of exciting things going on at 
Counterpane.  I can't talk about any of it yet, because we're still working 
on press releases.  We acquired SDII, a small consulting company.
<http://www.counterpane.com/pr-sdiacquisition.html>
More news next month.

Articles on Counterpane have appeared in The New York Times and The Economist:
<http://www.nytimes.com/2001/04/18/technology/18SCHW.html>
<http://www.economist.com/business/displayStory.cfm?Story_ID=569825>

eWeek reported on Schneier's talk at the RSA Conference last month:
<http://www.zdnet.com/eweek/stories/general/0,11011,2705973,00.html>

Bruce Schneier is speaking at ISSA events in New York (May 17), Palo Alto 
(Jun 6), and Denver (Jun 14):
<http://www.nymissa.org/documents/ISSA_2001_F_425.pdf>
<http://www.issa.org>

Schneier is speaking at the Trema World Forum in Monaco on May 30:
<http://www.trema-world-forum.com/>

_Secrets and Lies_ won a "Jolt" award from Software Development magazine:
<http://www.sdmagazine.com/features/jolts/>
<http://www.counterpane.com/pr-joltaward.html>

And Counterpane is still hiring:
<http://www.counterpane.com/jobs.html>


** *** ***** ******* *********** *************

               Security Standards



Andrew Tanenbaum once quipped that the great thing about standards is that 
there are so many to choose from.  Despite numerous efforts over the years 
to develop comprehensive computer security standards, it's a goal that 
remains elusive at best.

It all started with the Orange Book.  As far back as 1985, the U.S. 
government attempted to establish a general method for evaluating security 
requirements.  This resulted in the "Orange Book," the colloquial name for 
the U.S. Department of Defense Trusted Computer System Evaluation 
Criteria.  The Orange Book gave computer manufacturers a way to measure the 
security of their systems and offered a method of classifying different 
levels of computer security.

The goal was to aid government procurement, but it also held the promise of 
benefiting the entire industry as well.  That never came to pass, primarily 
because certification testing was expensive and controlled by a only few 
labs, and the resulting designations weren't well-suited to the civilian 
marketplace's needs.

There have been other efforts over the years to codify security, but they 
were unsuccessful.  Now, several industries are rallying around the Common 
Criteria, an ISO standard (15408, version 2.1) that provides a catalog of 
security features such as confidentiality and authentication.  Companies 
and industries using this document are expected to include these concepts 
in a more specific "protection profile," which is basically a statement of 
security requirements.

Then, individual products can be tested against that profile.  For example, 
a smart card could be tested against a protection profile with such 
attributes as resistance to cloning, security of protocols and protection 
against physical reverse engineering, and a firewall could have a different 
protection profile that includes attributes related to its security and 
functionality.

It's a great idea, and puts more meat on the bone than past efforts.  But 
don't expect it to work except in a few isolated areas.  The problem is 
that these standards are too general.  They won't tell you how to configure 
your CheckPoint firewall, or what security settings to run on Windows 
2000.  It's not a shortcoming in the standards; it's just not feasible to 
document an infinite number of scenarios.

Consider something truly quantitative: say, a configuration guide on the 
best way to secure Red Hat Linux 6.0.  It could be an excellent standard, 
but it will probably be obsolete in a few weeks.  It will certainly have to 
be revised for version 6.1.  And it can't possibly help you configure 
Solaris version 3.2, let alone Windows NT SP 4.0.

On the other hand, some standards can be too specific, making it almost 
impossible to test a general system.  Remember when Windows NT received the 
Orange Book's C2 security rating?  The rating was only good for a specific 
configuration of Windows, one unconnected to the network and without any 
removable media.  What about a rating for the overall security of Windows 
NT?  Forget about it!

The bottom line is that while these standards can be very useful for 
certain applications, they aren't useful gauging enterprise security in 
general.  The Common Criteria is a great document, and companies like Visa 
are putting a lot of effort to turn it into something that they can use for 
their own purposes.  The credit card company is currently using the 
document to specify security levels of hardware and software.  But that's 
only a special case; no one else can take what Visa did and make use of it.

I have long joked that given any general security standard, I could design 
a product that 1) met the standard, and 2) was still insecure.  Given this 
truism, it's no wonder that these standards don't find much utility in the 
commercial world.  And it's no wonder why there are so many standards to 
choose from.

Common Criteria:
<http://www.commoncriteria.org>

NSA's Rainbow Series, including the Orange Book:
<http://www.radium.ncsc.mil/tpep/library/rainbow>

There are configuration guides that are designed to help you with specific 
products.  This SANS Windows NT guide is an excellent example:
<http://www.sans.org/newlook/publications/ntstep.htm>
So is Phil Cox's Windows 2000 guide:
<http://www.systemexperts.com/win2k.shtml>


** *** ***** ******* *********** *************

            Safe Personal Computing



I am regularly asked what the average Internet user can do to ensure his 
security.  My first answer is usually "Nothing; you're screwed."  But it's 
really more complicated than that.

Against the government there's nothing you can do.  The power imbalance is 
just too great.  Even if you use the world's best encryption, the police 
can install a keyboard sniffer while you're out.  (If you're paranoid 
enough to sleep with your gun and laptop under your pillow, this article is 
not written for you.)  Even big corporations are difficult to defend 
against.  If they have your credit card number, for example, there's 
probably no way to make them forget it.

But there are some things you can do to increase your security on the 
Internet.  None of these are perfect; none of these are foolproof.  If the 
secret police wants to target your data or your communications, none of 
these will stop them.  But they're all good network hygiene, and they'll 
make you a more difficult target than the computer next door.

1.  Passwords.  You can't memorize good enough passwords any more, so don't 
bother.  Create long random passwords, and write them down.  Store them in 
your wallet, or in a program like Password Safe.  Guard them as you would 
your cash.  Don't let Web browsers store passwords for you.  Don't transmit 
passwords (or PINs) in unencrypted e-mail and Web forms.  Assume that all 
PINs can be easily broken, and plan accordingly.

2.  Antivirus software.  Use it.  Download and install the updates every 
two weeks, and whenever you read about a new virus in the media.  Some 
antivirus products automatically check for updates.

3.  Personal firewall software.  Use it.  There's usually no reason to 
allow any incoming connections from anybody.

4.  E-mail.  Delete spam without reading it.  Don't open, and immediately 
delete, messages with file attachments unless you know what they 
contain.  Don't open, and immediately delete, cartoons, videos, and similar 
"good for a laugh" files forwarded by your well-meaning friends.  Turn off 
HTML mail.  Don't use Outlook or Outlook Express.  If you must use 
Microsoft Office, enable macro virus protection; in Office 2000, turn the 
security level to "high" and don't trust any sources unless you have 
to.  If you're using Windows, turn off the "hide file extensions for known 
file types" option; it lets Trojan horses masquerade as other types of 
files.  Uninstall the Windows Scripting Host if you can get along without 
it.  If you can't, at least change your file associations so that script 
files aren't automatically sent to the Scripting Host if you double-click them.

5.  Web sites.  SSL does not provide any assurance that the vendor is 
trustworthy or that their database of customer information is 
secure.  Think before you do business with a Web site.  Limit financial and 
personal data you send to Web sites; don't give out information unless you 
see a value to you.  If you don't want to give out personal information, 
lie.  Opt out of marketing notices.  If the Web site gives you the option 
of not storing your information for later use, take it.

6.  Browsing.  Limit use of cookies and applets to those few sites that 
provide services you need.  Regularly clean out your cookie and temp 
folders (I have a batch file that does this every time I boot.)  If at all 
possible, don't use Microsoft Internet Explorer.

7.  Applications.  Limit the applications on your machine.  If you don't 
need it, don't install it.  If you no longer need it, uninstall it.  If you 
need it, regularly check for updates and install them.

8.  Backups.  Back up regularly.  Back up to disk, tape, or CD-ROM.  Store 
at least one set of backups off-site (a safe-deposit box is a good place) 
and at least one set on-site.  Remember to destroy old backups; physically 
destroy CD-R disks.

9.  Laptop security.  Keep your laptop with you at all times when not at 
home; think of it as you would a wallet or purse.  Regularly purge unneeded 
data files from your laptop.  The same goes for palm computers; people tend 
to keep even more personal data, including passwords and PINs, on them than 
on laptops.

10.  Encryption.  Install an e-mail and file encryptor (like 
PGP).  Encrypting all your e-mail is unrealistic, but some mail is too 
sensitive to send in the clear.  Similarly, some files on your hard drive 
are too sensitive to leave unencrypted.

11.  General.  Turn off the computer when you're not using it, especially 
if you have an "always on" Internet connection.  If possible, don't use 
Microsoft Windows.

Honestly, this is hard work.  Even I can't say that I diligently follow my 
own advice.  But I do mostly, and that's probably good enough.  And 
"probably good enough" is about the best you can do these days.


** *** ***** ******* *********** *************

             Comments from Readers



From: David Wallace <david.wallace@sabre.com>
Subject:  Military History and Computer Security

I was taken aback by your assertion that a burglar alarm works because "the 
attacker doesn't know they're there."  After all, "true victory consists of 
breaking the enemy's will without fighting."  The first line of defense is 
deterrence, the number one reason for installing a burglar alarm.  Security 
starts with making yourself a more difficult target.  Hence the "Premises 
protected by" stickers in windows and "Alarm" signs in front yards.  They 
encourage a potential attacker to pick another, less heavily defended, 
target.  In fact, the target may be completely undefended, protected only 
by signage purchased at a hardware or department store.

The Internet makes deterrence a little more dicey.  First off, the alarm is 
necessary, but the "alarm" sign is impractical.  It is a potential "red 
cape" waved at a hacking "bull."  It may also tip the defender's hand by 
revealing his defenses.  In the physical realm there are a wide variety of 
systems and sensors to deploy to "measure."  In the virtual, there are 
fewer, they are less easily understood, and harder to install and configure.

Once deterrence fails, detection becomes key.  In the physical world, the 
alarm system monitors a variety of metrics to evaluate defensive posture 
(system armed/unarmed), readiness to respond (sensor 
operational/deactivated), and violations of its sensors (heat, motion, 
noise, moisture, or sensor loss).  The Internet alarm performs the same 
functions, and performs them in much the same way.

The next step in deterrence is the concept of "unacceptable losses".  Here 
the two worlds both converge and diverge.  They converge on the definition 
of unacceptable losses.  On both the physical and logical plane 
unacceptable losses include arrest, conviction, fine, and/or 
imprisonment.  They diverge in the likelihood of suffering unacceptable losses.

As you note in _Secrets and Lies_, in physical security, the attacker must 
be physically present, rendering him not only detectable, but visible, and 
apprehend able.  The Internet removes that risk from the attacker, allowing 
him to strike remotely and in relative anonymity.

Once attacked, there are two phases to the defense: Repel and 
counterattack.  In the physical world, once an attacker is repelled, you 
follow up with counterattack.  Repelling the attack is accomplished by 
holding ground and buying time while the resources needed to stop the 
attack are marshalled and committed (amateurs debate tactics, professional 
soldiers argue logistics).

Counterattack is accomplished by understanding the attacker's objective and 
the resources he has committed to the attack.  The defender manipulates 
these variables to expose vulnerabilities in the attacker's position which 
can be exploited.  These can weaken the enemy, forestall his attack, and 
potentially force his retreat.  If retreat can be forced, it can be 
followed up with pursuit, further weakening the attacker, deterring future 
aggression, and potentially reducing the attacker's resources below the 
level necessary to support another assault.

Unfortunately, counterattack and pursuit do not transfer well to the 
virtual battlefield.  About the only option is to repel.  The logical 
version of counterattack is limited to prosecution, which proves difficult 
when attacks occur across state and national boundaries.  Even when 
prosecution does occur, it is hampered by poor forensics, poor laws, and 
general ignorance within the court system (See the judge in the Mittnick 
trial).

So what can you do to defend? Roll deterrence into your 
defense.  Monitor.  REVIEW THE LOGS! Have an incident response 
plan.  Partner with law enforcement and a professional forensics team.  Be 
prepared to go public when attacked.  Aggressively prosecute intruders 
whenever possible.  Develop a reputation as a target to stay away from.


From: Henry Spencer <henry@spsystems.net>
Subject:  Military History and Computer Security

I would argue that there's a third issue, more important on the military 
side although it's not clear that there is any useful Internet 
analogy.  Another old military axiom: "the attacker must vanquish; the 
defender need only survive."

The defender's biggest advantage is that the attack has to make progress to 
succeed, and the defense doesn't.  This puts the attacker out in the open, 
moving forward, while the defender is stationary and under cover -- less 
visible, better protected, and much more easily connected to communications 
and supply lines.

This shows, for example, in a traditional distinction between two types of 
hand grenades:  offensive and defensive.  An offensive grenade has a rather 
limited lethal radius, because it's meant to be used by attackers, who may 
be on the move or behind poor cover; in particular, it relies more on blast 
than on fragmentation.  A defensive grenade is designed to be lethal over 
the widest possible area, for use by people who are safely ensconced behind 
solid cover and may be (locally) badly outnumbered.  (I am not sure this 
distinction is still made nowadays, since even defensive forces now tend to 
emphasize mobility, but at one time it was taken quite seriously.)


From: "Gerard Joseph" <gerard@au1.ibm.com>
Subject:  Military History and Computer Security

I keep thinking about the apportionment of blame between the innocent 
defender and the guilty attacker.  Presumably, a bank robber would still be 
charged and found guilty even if one night the bank completely forgot to 
lock its doors or set its alarms.  But in that case I'm sure the bank would 
be held partly responsible for the attack.  If someone takes a shot at me 
while I'm ambling on the street, then he will always be guilty, even though 
I might have been negligent in walking on that particular street at that 
particular time.  It seems that in all cases there develops, over time and 
in accordance with local norms and experience, a state of equilibrium 
between the rate of crime and the level of defenses that are customarily 
implemented to thwart criminal acts.  Ideally, this state represents an 
optimal balance between the level of crime and the cost of relevant 
defensive measures.  A criminal who succeeds in spite of those defenses is 
more readily seen to be guilty, while a victim who falls short in 
implementing accepted levels of defense is less readily seen to be 
innocent.  But in no case does the victim's negligence excuse or justify 
the crime, nor does the criminal's ability to overcome your defenses excuse 
or justify their absence.

I think as far as the Internet is concerned, we are groping towards the 
defining equilibrium between crime and defense.  Right now, there is a set 
of protective measures whose omission would certainly represent culpability 
on the part of a defender, and there is a set of attacks whose commission 
would certainly represent a crime (whether legally recognized or not) on 
the part of the attacker.  But in between there is a grey area of defenses 
and attacks that lack categorical classification.  To date, though, I think 
we've been too lenient on both complacent defenders and aggressive 
attackers.  That must and surely will change.  A starting point would be 
for the media to stop interviewing hackers as if they were just ordinary 
community-minded citizens.


From: Stephen Tye <StephenT@marshalsoftware.com>
Subject: e-mail filter idiocy

I have read your article and I can understand your annoyance at having your 
e-mail blocked for containing the unrelated words "blow" and "job".  I 
admit the sample text censor scripts that we provided in MailMarshal 
version 3.3 have a couple of anomalies like this that would false 
trigger.  We have done a lot of work on our sample text censor scripts for 
the next version release to improve them and minimize false triggers.

MailMarshal is a tool to allow companies to apply corporate policy to their 
e-mail.  Technically MailMarshal did exactly what it was told to do, which 
was to block e-mails with the words blow and job in them.  In this case it 
was the script that was at fault, not the product.

Depending on how the company has set up our product to match their 
corporate guidelines, it is highly likely that the intended recipient of 
your e-mail also received a notification e-mail informing them that your 
e-mail did not arrive.   The e-mail you sent would have most likely been 
quarantined and could have been easily released by the administrator.  The 
line "blow and job" could have then been removed from the text censor 
script and the problem would never occur again.

If it is the organization's policy to block any e-mails which contain the 
words "IL*VEYOU" in the subject, then that is their choice and MailMarshal 
will allow them to enforce that policy.  We normally only suggest using a 
text censor script in this way when there is a virus alert and you would 
like implement some protection until you can get your antivirus product 
updated.  Otherwise we find scanning e-mails with an antivirus product and 
implementing rules that block e-mails which contain EXE or VBS attachments 
(which normally have no business use for end users) an effective protection 
against e-mail borne viruses.

As you well know, security is process, not product.  MailMarshal is a tool 
that allows you to apply that process.  It will only action what it has 
been told to do.


** *** ***** ******* *********** *************

CRYPTO-GRAM is a free monthly newsletter providing summaries, analyses, 
insights, and commentaries on computer security and cryptography.

To subscribe, visit <http://www.counterpane.com/crypto-gram.html> or send a 
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Please feel free to forward CRYPTO-GRAM to colleagues and friends who will 
find it valuable.  Permission is granted to reprint CRYPTO-GRAM, as long as 
it is reprinted in its entirety.

CRYPTO-GRAM is written by Bruce Schneier.  Schneier is founder and CTO of 
Counterpane Internet Security Inc., the author of "Secrets and Lies" and 
"Applied Cryptography," and an inventor of the Blowfish, Twofish, and 
Yarrow algorithms.  He served on the board of the International Association 
for Cryptologic Research, EPIC, and VTW.  He is a frequent writer and 
lecturer on computer security and cryptography.

Counterpane Internet Security, Inc. is a venture-funded company bringing 
innovative managed security solutions to the enterprise.

<http://www.counterpane.com/>

Copyright (c) 2001 by Counterpane Internet Security, Inc.