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    Computer Crimes


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    1 : 1 “The public streets and highways of the internet have become like neighborhoods where it is no longer safe to venture. Hackers, scammers, virus builders and other Web predators are looming in the shadows.” -- Paul Tinnirello CIO in an insurance financial industry “The Gated Community”, e-Week, 13 Oct 2003
    2 : Computer Crimes An information session for participants in the 57-201 Introduction to Forensic Science course Akshai Aggarwal School of Computer Science
    3 : 3 Flow of the session Historical perspective 4-14 Threats and Attacks 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.
    4 : 4 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
    5 : 5 Types of Non-authorized Users 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:
    6 : 6 Terminology of Hacking 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
    7 : 7 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
    8 : 8 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)
    9 : 9 A little history (continued) Earlier in 1499 he had written a 3-book “Steganographia”, (meaning covered writing): 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.
    10 : 10 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.”
    11 : 11 “Ban, what you don’t understand.” 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.
    12 : 12 A little history: Deciphering the third book of Trithemius 1996:Thomas Ernst, Prof of German at La Roche College, Pittsburgh published a 200-page German-language 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.
    13 : 13 The first attack The Internet Worm (Nov 1988) Morris, a graduate student at CMU released a program on the internet: 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
    14 : 14 The first conviction Mitnick and Shimomura (Christmas 1994) 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.
    15 : 15 “….there will be more security breaches”, says Schneier As more of our infrastructure moves online, as more things, that someone might want to access or steal, move online ……. As our networking systems become more complex ….. As our computers get more powerful and more useful…..
    16 : 16 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
    17 : 17 Causes of Security Problems on Internet 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
    18 : 18 Security Threats RFC 1244 identifies three distinct types of security threats associated with network connectivity: 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.
    19 : 19 Classification of Security Threats Reference: RFC 1244 Disclosure of information disclosure of valuable or sensitive information to people, who should not have access to the information. Denial of service or Degradation of service Any problem that makes it difficult or impossible for the system to continue to perform productive work. Do not connect to Internet: a system with highly classified information, or, if the risk of liability in case of disclosure is great.
    20 : 20 Brent Chapman’s Three Categories of Security Threats Brent Chapman’s Classification: Confidentiality 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
    21 : 21 Information Security Threats Chapman’s Classification (contd.) availability: A DoS attack may disrupt 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.
    22 : 22 Loss Breakdown Reference: Jim Alves-Foss , Center for Secure and Dependable Systems, Univ of Idaho,
    23 : 23 Types of Attacks Attacks on computer systems using the computers Web-site defacement or Revealing the data to unauthorized persons/theft of sensitive information/ stealing information having Intellectual Property Rights like stealing credit card numbers bank frauds or Damage to data through Hacking or Virus/Worms
    24 : 24 Types of Attacks continued Hoax Letters: 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
    25 : 25 Types of Attacks propagate false routing entries (“black holes” and “sink holes”,, 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).
    26 : 26 A Web site,, 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. 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)
    27 : 27 An Example: time-to-market for Internet Security products 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
    28 : 28 Other Computer Crimes 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)
    29 : 29 ‘To be an effective Information Warrior, individuals need superior computer skills, as well as an in-depth understanding of information technology architectures,… protocols and processes.’ --- Michael Erbschloe author of “Information Warfare: How to Survive Cyber Attacks”
    30 : 30 General Strategies for security encrypting sensitive data reduce size of target: disable unneeded services limit access of attacker to target systems hardening the OS and applications
    31 : 31 “It is insufficient to protect ourselves with laws; we need to protect ourselves with mathematics.” ---Bruce Schneier in ‘Applied Cryptography’
    32 : 32 CRYPTOGRAPHY Cryptography (from two words in Greek): means secret writing. Cryptoanalysis: breaking of a cryptographic code CRYPTOGRAPHY: process data into unintelligible form, reversibly/irreversibly without data loss usually one-to-one in size /compression
    33 : 33 Cryptography Services, provided by cryptographic tools: 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 Encryption Algorithm Plaintext Key Ciphertext
    34 : 34 Encryption Two types of Encryption Algorithms Reversible Irreversible Two types of Keys Symmetric Assymetric
    35 : 35 Reversible Encryption Reversible ENCRYPTION: cleartext ENCRYPTION DEVICE encryption key cleartext can be used only when the same type of encryption software/equipment is available at both the ends ciphertext Decryption Device Decryption key
    36 : 36 Decryption Decryption or Deciphering Decryption Algorithm Ciphertext Plaintext Key
    37 : 37 Cryptographic Hash Functions (H) 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. H(m) m h
    38 : 38 Message Digest (recapitulation) Variable Length Message Hashing Algorithm Fixed Length Digest
    39 : 39 Secret Key/ Symmetric Cryptography 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
    40 : 40 Symmetric Key Encryption Also called Private/Secret key Encryption Sender-end Message by sender Message at receiver Pr-key Pr-key Encrypted Message Encrypted Message Internet Receiver-end
    41 : 41 public-key cryptography (continued)
    42 : 42 Asymmetric Key Encryption Also called Public key Encryption Message Message B’s public B’s private Encrypted Message Encrypted Message Internet A B key key
    43 : 43 public-key cryptography (continued) Data transmission: private key(d), public key (e)
    44 : 44 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
    45 : 45 Digital certificate for getting Public Key reliably A digital certificate from a trusted party may contain: 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: or (Verisign’s liability limited to $100 only!) Standard for certificate: X.509
    46 : 46 Digital signatures Digital Signatures: A is to sign a Msg and send it to B Msg Msg Msg + Encoded Digest Digest Algorithm Msg + Encoded Digest Digest Algorithm Decode digest using Public key of A Encoding using Private key of A Digest Digest Compare B A
    47 : 47 Laws and Group Efforts in Canada 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.
    48 : 48 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 1.2vN values. Function Random input 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
    49 : 49 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.
    50 : 50 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.
    51 : 51 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.
    52 : 52 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.
    53 : 53 To Intrusion Detection Analysts “Folks! You are the trackers of the 21st century. The signs are there, plain as day. It is up to you to find them and give the interpretation.” Stephen Northcutt
    54 : 54 References: The Trithemius riddle :1. Thomas (Penn) Leary,” Cryptology in the 16th and 17th Centuries”, Cryptologia, July 1996, available at 2. 3. Gina Kolata, ”A Mystery Unraveled, Twice”, The New York Times, April 14, 1998, pp. F1, F6, available at Hoax letters:

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