Transcript Lecture 1: Computer Security Overview

Lecture 1: Information
Security Overview
SYCS 653 – Fall 2009
Wayne Patterson
Attack of the Giant Worm

On November 2, 1988, a worm began to thread its way
through the Internet. Once installed, it multiplied,
clogging available space, until computers ground to a
halt. The worm exploited UNIX holes in sendmail and
fingerd. Around 2500 computers were infected.
Within 12 hours, the Computer Systems Research
Group at Berkeley developed a way of stopping the
spread of this worm.
Total Cost? Although no data were destroyed, the time
involved in fixing and testing was estimated to be
between $1,000,000 and $100,000,000.
The Culprit?

Robert J. Morris, a
Cornell graduate
student in computer
science, was
convicted on May 4,
1990 to 3-year
probation and a
$10,000 fine.

“I'm at the MIT
Computer Science
and Artificial
Intelligence
Laboratory (CSAIL) in
the PDOS group.
First National Attack
For the first time, a national attack on the
Internet was exposed.
 As a result, the Computer Emergency
Response Team (CERT), at the Software
Engineering Institute of Carnegie Mellon
University was developed.

Other Examples

Some other examples of
destructive computer behavior
include:
Cuckoo’s Egg: Clifford Stoll
spent a year tracking down a
hacker in West Germany who had
successfully penetrated 30
computers, including the
Lawrence Berkeley Labs, and
other government computers.
(The Cuckoo's Egg: Tracking a
Spy through the Maze of
Computer Espionage by Cliff
Stoll, Doubleday 1989.)
Other Examples


HBO: In April of 1986, an HBO channel was taken over
by an intruder known as Captain Midnight, who
overpowered the HBO uplink transmitter signal with a
stronger signal, and sent out his own messages to eight
million viewers.
Friday the 13th: A student at Hebrew University in
Jerusalem discovered that thousands of university
computers were infected with a virus. The virus slowed
down processing on certain Fridays the 13th and was
scheduled to erase the hard disks of many computers on
May 13, 1988.
Computer Crime

According to the FBI, computer crime is the most
expensive form of crime, at $450,000 per theft. The
estimated total volume of computer crime is
$5,000,000,000 per year.

Some reports estimate that 90% of computer crime goes
unreported.

(See http://www.usdoj.gov/criminal/cybercrime/cccases.html,
the Computer Crime & Intellectual Property Section of the US
Department of Justice, Computer Crime Cases.)
What is Computer Security?



Computer security is designed to protect your computer and
everything associated with it --- the building, the workstations and
printers, cabling, and disks and other storage media. Most
importantly, computer security protects the information stored in your
system.
Computer security is not only designed to protect against outside
intruders who break into systems, but also dangers arising from
sharing a password with a friend, failing to back up a disk, spilling a
soda on a keyboard.
There are three distinct aspects of security: secrecy, accuracy, and
availability.
Having said this, we should emphasize that “Information Security” or
“Cybersecurity” is more up-to-date terminology, since rarely are we
concerned with the protection of a single computer system.
Secrecy

A secure computer system must not allow information to
be disclosed to anyone who is not authorized to access
it. In highly secure government systems, secrecy
ensures that users access only information they’re
allowed to access.

In business environments, confidentiality ensures the
protection of private information such as payroll data.
Accuracy, Integrity, and
Authenticity

A secure computer system must maintain the continuing
integrity of the information stored in it. Accuracy or
integrity means that the system must not corrupt the
information or allow any unauthorized malicious or
accidental changes to it.

In network communications, a related variant of accuracy
known as authenticity provides a way to verify the origin
of data by determining who entered or sent it, and by
recording when it was sent and received.
Availability

A secure computer system must keep
information available to its users. Availability
means that the computer system’s hardware and
software keeps working efficiently and that the
system is able to recover quickly and completely
if a disaster occurs.
The opposite of availability is denial of service.
Denial of service can be every bit as disruptive
as actual information theft.
Threats to Security

There are three key words that come up in discussions of computer
security:






vulnerabilities,
threats, and
countermeasures.
A vulnerability is a point where a system is susceptible to attack.
A threat is a possible danger to the system: e.g. a person, a thing (a
faulty piece of equipment), or an event (a fire or a flood).
Techniques for protecting your system are called countermeasures.
Vulnerabilities

Examples:
physical vulnerabilities
natural vulnerabilities
hardware and software vulnerabilities
media vulnerabilities
emanation vulnerabilities
communications vulnerabilities
human vulnerabilities

There is a lot of variation in how easy it is to exploit different types of
vulnerabilities. For example, tapping a cordless telephone or a
cellular mobile phone requires only a $199 scanner from Radio
Shack.
Threats

Threats fall into three main categories:
natural threats
unintentional threats
intentional threats
The intentional threats can come from insiders or
outsiders. Outsiders can include:
foreign intelligence agents
terrorists
criminals
corporate raiders
crackers
Inside or Outside?

Although most security mechanisms
protect best against outside intruders,
survey after survey indicates that most
attacks are by insiders. Estimates are that
as many as 80% of system penetrations
are by fully authorized users.
The Insider

There are a number of different types of insiders:
disgruntled employee, the coerced employee,
and the greedy employee. One of the most
dangerous types of insiders may simply be lazy
or untrained. He or she doesn’t bother changing
passwords, doesn’t learn how to encrypt files,
doesn’t get around to erasing old disks, and
leaves sensitive printout in piles on the floor.
Countermeasures

There are many different types of
countermeasures ,methods of protecting
information. In the next several lectures,
we will survey these methods:
computer security
communications security
physical security
Information and Its Controls


Information security is almost as old as information itself.
innovations are inevitably followed by methods of harnessing the
new technologies and protecting the information they process.

within five years of the introduction of the telephone in 1881, a patent
applications was filed for a voice scrambler;

in the 1920s, the use of telephone wiretaps by government and
criminals resulted in a public outcry, leading to legislation banning most
wiretapping;

in the 1940s, concerns about controlling the proliferation of information
about atomic energy led to the Atomic Energy Act of 1946. This act
created a Restricted Data category of information requiring special
protection.
Debates




One ongoing debate in the computer security world is over the
government’s restriction of technological information.
The government needs to protect certain kinds of information,
such as national defense data.
Particular security technologies, for example, cryptology, are
very effective at safeguarding such information. Should the
government be able to control who can and cannot buy such
technologies?
Another debate concerns the involvement of the government in
mandating the protecting of nongovernment information.
Computer Security: Then and
Now



In the early days of computing, computer systems were
large, rare, and very expensive. Those organizations
lucky enough to have a computer tried their best to
protect it. Computer security was just one aspect of
general plant security.
Security concerns focused on physical break-ins, theft of
computer equipment, and theft or destruction of disk
packs, tape reels, and other media.
Insiders were also kept at bay. Few people knew how to
use computers, and thus the users could be carefully
screened.
Later On

By the 1970s, technology was transformed, and with it the ways in
which users related to computers and data. Multi-programaming,
time-sharing, and networking changed the rules.

Telecommunications --- the ability to access computers from remote
locations --- radically changed computer usage. Businesses began
to store information online. Networks linked minicomputers together
and with mainframes containing large online databases. Banking
and the transfer of assets became an electronic business.
New Abuses

The increased availability of online systems and information led to
abuses. Instead of worrying only about intrusions by outsiders into
computer facilities and equipment, organizations now had to worry
about

computers that were vulnerable to sneak attacks over telephone lines,
and
 information that could be stolen or changed by intruders who didn’t
leave a trace.

Individuals and government agencies expressed concerns about the
invasion of privacy posed by the availability individual financial,
legal, and medical records on shared online databases.
The PC World

The 1980s saw a new dawn in computing. With the
introduction of the PC, individuals of all ages and
occupations became computer users. This technology
introduced new risks. Precious and irreplaceable
corporate data were now stored on diskettes, which
could now be lost or stolen.

As PCs proliferated, so too did PC networks, electronic
mail, chat rooms, and bulletin boards, vastly raising the
security stakes. The 1980s also saw systems under
attack.
The Future

The challenge of the next decade will be to
consolidate what we’ve learned --- to build
computer security into our products and our
daily routines ,to protect data without
unnecessarily impeding our access to it, and to
make sure that both products and standards
grow to meet the ever-increasing scope of
challenge of technology.
Introduction to Crypto
The Cast of Characters

Alice and Bob are the good guys

Trudy is the bad guy

Trudy is our generic “intruder”
Alice’s Online Bank





Alice opens Alice’s Online Bank (AOB)
What are Alice’s security concerns?
If Bob is a customer of AOB, what are his
security concerns?
How are Alice and Bob concerns similar? How
are they different?
How does Trudy view the situation?
CIA
Confidentiality, Integrity, and Availability
 AOB must prevent Trudy from learning
Bob’s account balance
 Confidentiality: prevent unauthorized
reading of information

CIA
Trudy must not be able to change Bob’s
account balance
 Bob must not be able to improperly
change his own account balance
 Integrity: prevent unauthorized writing of
information

CIA


AOB’s information must be available when
needed
Alice must be able to make transaction
 If


not, she’ll take her business elsewhere
Availability: Data is available in a timely
manner when needed
Availability is a “new” security concern
 In
response to denial of service (DoS)
Beyond CIA
How does Bob’s computer know that “Bob”
is really Bob and not Trudy?
 Bob’s password must be verified

 This
requires some clever cryptography
What are security concerns of pwds?
 Are there alternatives to passwords?

Beyond CIA






When Bob logs into AOB, how does AOB know
that “Bob” is really Bob?
As before, Bob’s password is verified
Unlike standalone computer case, network
security issues arise
What are network security concerns?
Protocols are critically important
Crypto also important in protocols
Beyond CIA

Once Bob is authenticated by AOB, then AOB
must restrict actions of Bob
 Bob
can’t view Charlie’s account info
 Bob can’t install new software, etc.


Enforcing these restrictions is known as
authorization
Access control includes both authentication
and authorization
Beyond CIA


Cryptography, protocols, and access control
are implemented in software
What are security issues of software?
 Most
software is complex and buggy
 Software flaws lead to security flaws
 How to reduce flaws in software development?
Beyond CIA

Some software is intentionally evil
 Malware:
computer viruses, worms, etc.
What can Alice and Bob do to protect
themselves from malware?
 What can Trudy do to make malware more
“effective”?

Beyond CIA

Operating systems enforce security
 For

example, authorization
OS: large and complex software
 Win
XP has 40,000,000 lines of code!
 Subject to bugs and flaws like any other software
 Many security issues specific to OSs
 Can you trust an OS?
The Textbook

The text consists of four major parts
 Cryptography
 Access
control
 Protocols
 Software
 In
this course, we will address the first two of
these (the others in 654)
Cryptography
“Secret codes”
 The book covers

 Classic
cryptography
 Symmetric ciphers
 Public key cryptography
 Hash functions
 Advanced cryptanalysis
Access Control

Authentication
 Passwords
 Biometrics

and other
Authorization
 Access
Control Lists and Capabilities
 Multilevel security (MLS), security modeling, covert
channel, inference control
 Firewalls and Intrusion Detection Systems
Think Like Trudy
In the past, no respectable sources talked
about “hacking” in detail
 It was argued that such info would help
hackers
 Very recently, this has changed

 Books
on network hacking, how to write evil
software, how to hack software, etc.
Think Like Trudy
Good guys must think like bad guys!
 A police detective

 Must

study and understand criminals
In information security
 We
want to understand Trudy’s motives
 We must know Trudy’s methods
 We’ll often pretend to be Trudy
Think Like Trudy
Is all of this security information a good
idea?
 “It’s about time somebody wrote a book to
teach the good guys what the bad guys
already know.”  Bruce Schneier

Think Like Trudy
We must try to think like Trudy
 We must study Trudy’s methods
 We can admire Trudy’s cleverness
 Often, we can’t help but laugh at Alice and
Bob’s stupidity
 But, we cannot act like Trudy

In This Course…
Always think like the bad guy
 Always look for weaknesses
 Strive to find a weak link
 It’s OK to break the rules
 Think like Trudy!
 But don’t do anything illegal…
