Computer Crimes
An information session for participants in the 57-201
Introduction to Forensic Science course
Flow of the session
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Historical perspective 4-14
Threats and Attacks
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Threats 18-21
Types of Attacks 23-30
Technology of defence 32-50
Laws and group Efforts in Canada 51
A couple of general ideas, in conclusion
Note: Terminology may be explained, as the need
arises.
2
Historical Perspective: Terminology
1960s and 1970s:
Hacker: a positive term

A Hacker: An expert, knowledgeable about programming and
operating systems
1970s onwards:
Hacker: a term, which progressively became more negative.

A Hacker: Someone using computers without authorization
.
.
Hacker: Someone committing crimes by using computers
3
Types of Non-authorized Users
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Hacker: people who access a computer resource,
without authorization
Crackers: a hacker who uses his or her skills to
commit unlawful acts, or to deliberately create
mischief
Script Kiddies: a hacker who downloads the scripts
and uses them to commit unlawful acts, or to
deliberately create mischief, without fully
understanding the scripts.
Vandals
Reference:http://www.e2chameleon.btinternet.co.uk/hacking.htm
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Terminology of Hacking
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Eavesdropping or Snooping (also called
passive wire-tapping)
Active wire-tapping or man-in-the middle
attack
Dumpster Diving: colloquial for looking
through all the easily available material
before an actual intrusion into a system
5
The Global Net:
A Virtual Intelligent Global System
2 Sept 1969 LEN KLEINROCK’S Lab at UC,LA
1971 15 Nodes 23 Hosts
1973 BOB METCALFE’S thesis on
ETHERNET at Harvard
1974 TCP: CERF & BOB KAHN’S paper
1983 DoD Official Protocol.
1989 Hypertext & WWW at CERN by
Berner Lee

Then came the BROWSER’S MOSAIC NCSA
and the WWW
6
Security Technologies:
A little history of an ancient art:
The first printed book on cryptology
Johannes Trithemius, an abbot in Spanheim :
One of the founders of cryptology

The first printed book of cryptology: titled
“Polygraphiae Libri Sex “ in German language
in 1518 by Johannes Trithemius,published
after the death of the writer.
(The title means -Six Books of Polygraphy)
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A little history (continued)
Earlier in 1499 he had written a 3-book
“Steganographia”, (meaning covered writing):
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which was circulated privately
was published in 1606.
The first two books: about cryptology.
But the third book could not be understood,
without understanding the encoding that he
had used.
8
A little history (continued):
A challenge for a cryptanalyst

In the third book, which was considered to be
incomplete, Trithemius explained why he had made it
hard to understand:
“This I did that to men of learning and men
deeply engaged in magic, it might, by the
Grace of God, be in some degree intelligible,
while on the other hand, to the thick skinned
turnip-eaters it might for all time remain a
hidden secret, and be to their dull intellects a
sealed book forever.”
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“Ban, what you don’t understand.”
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The third book: banned in 1609, ostensibly
because it explained how to employ spirits for
sending secret messages.
The challenge - of deciphering the book: met by
three persons in 500 years
1676:Wolfgang Heidel, the archbishop of
Mainz, Germany, claimed to have deciphered
the third book of Trithemius.
But his discovery was stated in a secret code
of his own. So nobody knew whether Heidel
had understood the book.
10
A little history:
Deciphering the third book of Trithemius
1996:Thomas Ernst, Prof of German at La Roche
College, Pittsburgh published a 200-page Germanlanguage report in a small Dutch journal, Daphnis.
 WIDELY KNOWN SOLUTION: spring 1998: Jim
Reeds of AT & T labs solved the riddle of
understanding the third book independently.
He did not know of the earlier work of Ernst.
Trithemius work: basically simple: Ernst took two weeks
and Reeds took two days to understand it.
Both Ernst and Reeds, separately, deciphered Heidel’s
work and found that Heidel had been able to
decipher Trithemius’ third book.

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The first attack
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The Internet Worm (Nov 1988)
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Morris, a graduate student at CMU
released a program on the internet:
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utilized a security hole in the mail receipt
software
automatically replicated itself locally and to
remote machines
affected a wide class of machines and
effectively shut down internet for 1-2 days.
Cost estimate to fix: $5 million
12
The first conviction

Mitnick and Shimomura (Christmas
1994)
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Used SYN flooding and TCP Hijacking to
connect to Shimomura’s home machine.
Stole copies of 1000’s of files including
specialized computer security software;
modified log files to remove signs of entry.
Shimomura found out about the entry and
informed FBI.
13
Common attacks on banks
through Internet
Losses due to attacks:
"The major banks don't want to divulge
the amount of losses. But just to give
one example, a major Australian bank
has put several million dollars in reserve
since August 2003 to cover damages
due to Internet frauds.“– Dave Jevans,
eWeek, Dec 2003
14
Causes of Security Problems on Internet
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Internet Technology: was developed
based on trust
Security features: added, as different
types of attacks are mounted.
Users: bother about ease of use and
not about security
15
Security Threats
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RFC 1244 identifies three distinct types of
security threats associated with network
connectivity:
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Unauthorized access

A break-in by an unauthorized person.
Break-ins may be an embarrassment that
undermine the confidence that others have in
the organization.
Moreover unauthorized access  one of the
other threats:-- disclosure of information or
--denial of service.
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Classification of Security Threats
Reference: RFC 1244
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Disclosure of information

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disclosure of valuable or sensitive information to people,
who should not have access to the information.
Denial of service or Degradation of service
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Any problem that makes it difficult or impossible for the
system to continue to perform productive work.
Do not connect to Internet:
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a system with highly classified information, or,
if the risk of liability in case of disclosure is
great.
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Brent Chapman’s
Three Categories of Security Threats
Brent Chapman’s Classification:
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Confidentiality
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Of data
Of existence of data
Of resources, their operating systems, their
configuration
Of resources used, in case the resources are
taken on rent from a service provider
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Information Security Threats
Chapman’s Classification (contd.)
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availability: A DoS attack may disrupt
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availability of a service, or
availability of data
integrity
Of data
 Of origin:
Once someone has gained unauthorized access
to a system, the integrity of the information on
that system is in doubt.

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Loss Breakdown
Human error
55%
Outsider
attacks
2%
Physical
security
problems
20%
Viruses
4%
Dishonest
employees
10%
Disgruntled
employees
9%
Reference: Jim Alves-Foss , Center for Secure and Dependable Systems, Univ of Idaho,
http://www.cs.uidaho.edu/~jimaf/cs442/crime-talk.ppt
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Types of Attacks
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Attacks on computer systems using the computers
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Web-site defacement or
Revealing the data to unauthorized persons/theft of
sensitive information/ stealing information having
Intellectual Property Rights
like
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stealing credit card numbers
bank frauds or
Damage to data
through
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Hacking or
Virus/Worms
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Types of Attacks
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Hoax Letters:
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continued
Examples
Malicious code (viruses and trojan horses)
Urban myths
Scam letters to entrap the receiver
Internet gambling
Internet Pornography/ stalking
Link Flooding
Packet Intercepting, Password Sniffing
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Types of Attacks
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propagate false routing entries (“black holes” and
“sink holes”, www.citibank.com,
www.mybank.az)
domain name hijacking
Phishing attacks: use e-mails that often
appear to come from a legitimate e-mail
address and include links to spoofed Web
addresses. The receiver responds to the link,
which takes the receiver to a site, other than
what the receiver thinks he is going to.
(announced by MS on 16 Dec 2003, as a
problem with Internet Explorer).
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Anti-Phishing.org
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A Web site www.antiphishing.org,, for reporting
incidents, set up by a group of global banks and
technology companies, led by Secure-messaging firm
Tumbleweed Communications Corp
Fast Response required: The Web sites designed for
collecting personal information in phishing attacks
are often alive for a day only.
Example: Dec 2003:The e-mail appeared to come
from the U.K. bank NatWest.
Anti-Phishing.org tracked the IP address to a home
computer in San Francisco.
But a clear case of spoofing—the mail was relayed
from a hijacked computer (called a zombie)
24
An Example:
time-to-market for Internet Security products
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16 December, 2003: Discovery of the
problem of Phishing
5 January 2004: Announcement of
development of a new Anti-phishing
service by Netcraft, of Bath, England.
Netcraft says that the service is mainly for
banks and other financial organizations
25
Other Computer Crimes
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Spoofing or Masquerading of a host or a
service-provider (Distinguish it from
Delegation)
Repudiation of origin or of creation of some
file
Denial of receipt
Usurpation: unauthorized control
Data Diddling (To enter false data
intentionally)
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General Strategies for security
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encrypting sensitive data
reduce size of target:
disable unneeded services
limit access of attacker to target
systems
hardening the OS and applications
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CRYPTOGRAPHY
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Cryptography (from two words in Greek):
means secret writing.
Cryptoanalysis: breaking of a cryptographic
code
CRYPTOGRAPHY: process data into unintelligible
form,
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reversibly/irreversibly
without data loss
usually one-to-one in size /compression
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Cryptography
Services, provided by cryptographic tools:
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Encoding information into a form which makes the
information unintelligible to an unauthorized person
integrity checking: no tampering
authentication: not an impostor
Encryption or Enciphering
Plaintext
Encryption
Algorithm
Ciphertext
Key
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Encryption
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Two types of Encryption Algorithms
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Reversible
Irreversible
Two types of Keys
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Symmetric
Assymetric
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Reversible Encryption
Reversible ENCRYPTION:
cleartext
ENCRYPTION DEVICE
Decryption key
cleartext

ciphertext
encryption key
Decryption Device
can be used only when the same type
of encryption software/equipment is
available at both the ends
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Decryption
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Decryption or Deciphering
Ciphertext
Decryption
Algorithm
Plaintext
Key
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Cryptographic Hash Functions (H)
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H : A transformation: One way
m = variable size input
h = hash value : a fixed size string,
also known as message digest or fingerprint
or compression function.
m
H(m)
h
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Message Digest
Variable
Length
Message
Hashing
Algorithm
(recapitulation)
Fixed Length
Digest
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Secret Key/ Symmetric Cryptography
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Simpler and faster (than ?) and, of course, secure
For Integrity check, a fixed-length checksum for
the message may have to be used; CRC* not
sufficient
*Cyclic Redundancy Check
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Symmetric Key Encryption
Also called Private/Secret key Encryption
Message
by sender
Sender-end
Pr-key
Encrypted
Message
Internet
Message
at receiver
Pr-key
Encrypted
Message
Receiver-end
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public-key cryptography
(continued)
37
Asymmetric Key Encryption

Also called Public key Encryption
A
B’s public Encrypted
Message
Message
key
Internet
Message B’s private Encrypted
Message
key
B
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public-key cryptography
(continued)

Data transmission: private key(d), public
key (e)
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public-key cryptography
(continued)
Applications and Advantages:
 Storage: for safety: use public key of trusted
person
 Secret vs. Public Key system:
secret key system: needs secret key for every pair
of persons, that wish to communicate
n users  n(n-1)/2 keys
public key system: needs two keys for every
person, who wants to communicate.
n users  2n keys
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Digital certificate
for getting Public Key reliably

A digital certificate from a trusted party may
contain:
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The name of a person
His e-mail address
His public key
The recipient of the encrypted certificate uses
the public key of the Certification Authority to
decode the certificate.
Examples of CAs: www.verisign.com or
www.thawte.com (Verisign’s liability limited to
$100 only!)
Standard for certificate: X.509
41
Digital signatures
Digital Signatures: A is to sign a Msg and send
it to B

A
Msg
Digest
Algorithm
Msg +
Encoded
Digest
Encoding using
Private key of A
Msg +
Encoded
Digest
Decode digest using
Public key of A
B
Digest
Msg
Digest
Algorithm
Digest
Compare
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Laws and Group Efforts in Canada
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No separate cyberspace law in Canada
But the Canadian Criminal Code and the
Canadian Human Rights Act apply in
cyberspace.
The Internet Protection Portal, established by
the Canadian Association of Internet
Providers (CAIP): an on-line window to
resources for a user to safeguard the Internet
experience.
Media Awareness Network (MNet): supports
media education in Canadian homes, schools
and communities.
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Birthday paradox

A result from probability theory: Consider an element
that has an equal probability of assuming any one of
the N values. The probability of a collision is more
than 50% after choosing 1.2√N values.
Random input
Function
One of k equally
likely values
The same output can be expected after 1.2k1/2
inputs. Thus in a group of 23, two or more
persons are likely to share the same birthday.
(Put k = 365) Birthday attacks are used to find
collisions of Hash functions
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Example of a Birthday Attack
Assume
 A 64 bit key
 The first statement in a message is always the same.
A hacker
 listens to and stores all encrypted messages.
 When the FIRST encrypted sentence turns out to be
the same, he replaces the rest of the new message
by the old message, that he has in his memory.
By Birthday Paradox, this is likely to happen after 232
transactions.
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Cryptography vs. Steganography
Cryptography : uses techniques like
transpositions and substitution to make
a message unintelligible
 Steganography : hides the existence of
the method.
Cryptography provides privacy.
Steganography provides secrecy.
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Hiding a message in a picture


Described by Wyner in ‘Byte’
 Kodak photo CD resolution of 2048x3072 pixels.
 Each pixel: 24-bit RGB color information.
 Modify the last bit (out of 8 bits) for each color.
 Amount of data that can be hidden in a single picture:
2048 * 3072*3
= 2.359296 Mb = about 300,000B
10^6
If four bits of intensity for each of the three
colors RGB are altered  1.5 text characters
hidden in each pixel of the photo.
A 640x480 pixel image  can store over
400,000 characters, equal to a whole book.
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Steganography: Hiding Messages:
Example of a Laser printer
Another example: Laser printers can
adjust spacing of lines and characters
by less than 1/300th of an inch.
To hide a 0, leave a standard space.
To hide a 1, leave 1/300th of an inch
more than usual.
Varying the spacing over an entire document can
hide a short binary message that is undetectable
by the human eye.
The hidden message will be carried by every
photocopy of the document also.
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