Privacy - not readable• Permanent - not alterable (can't edit, delete)• Reliable - (changes detectable)

But the data must be accessible to persons authorized to:

• Read, edit, add, delete

Probably over a network, possibly over the Internet.

Objectives of Data Security(relative to unauthorized persons)

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* Security Attack: Any action that compromises the security of information.

* Security Mechanism: A mechanism that is designed to detect, prevent, or recover from a security attack.

* Security Service: A service that enhances the security of data processing systems and information transfers. A security service makes use of one or more security mechanisms.

Attacks, Services, and Mechanisms

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4

Security Services

* Confidentiality (privacy)

* Authentication (who created or sent the data)

* Integrity (has not been altered)

* Non-repudiation (the order is final)

* Access control (prevent misuse of resources)

* Availability (permanence, non-erasure)

- Denial of Service Attacks

- Virus that deletes files

5

Virus - code that copies itself into other programs

Payload - harmful things it does, after it has had time to spread.

Worm - a program that replicates itself across the network (usually riding on email messages or attached documents (e.g., macro viruses).

Trojan Horse - instructions in an otherwise good program that cause bad things to happen (sending your data or password to an attacker over the net).

Logic Bomb - malicious code that activates on an event (e.g., date).

Trap Door (or Back Door) - undocumented entry point written into code for debugging that can allow unwanted users.

Viruses, Worms, and Trojan Horses

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Have a well-known virus protection program, configured to scan disks and downloads automatically for known viruses.

Do not execute programs (or "macro's") from unknown sources (e.g., PS files, HyperCard files, MS Office documents, Java, ...), if you can help it.

Avoid the most common operating systems and email programs, if possible.

Virus Protection

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8

Password Gathering

Look under keyboard, telephone etc.

Look in the Rolodex under “X” and “Z”

Call up pretending to from “micro-support,” and ask for it.

“Snoop” a network and watch the plaintext passwords go by.

Tap a phone line - but this requires a very special modem.

Use a “Trojan Horse” program to record key stokes.

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The Stages of a Network Intrusion

1. Scan the network to:• locate which IP addresses are in use, • what operating system is in use, • what TCP or UDP ports are “open” (being listened to by Servers).

2. Run “Exploit” scripts against open ports3. Get access to Shell program which is “suid” (has “root” privileges).4. Download from Hacker Web site special versions of systems files that will let Cracker have free access in the future without his cpu time or disk storage space being noticed by auditing programs.5. Use IRC (Internet Relay Chat) to invite friends to the feast.

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Application Layer (HTTP)

Transport Layer(TCP,UDP)

Network Layer (IP)

E'net DataLink Layer

Ethernet

Phys. Layer

Network Layer

E'net DataLink Layer

E'net Phys.Layer

Network Layer

Web Server Browser

Router-Firewallcan drop packets

based onsource or destination,ip address and/or port

Application Layer (HTTP)

Transport Layer(TCP,UDP)

Network Layer (IP)

Token Ring

Data-Link Layer

Token RingPhys. Layer

IP Address130.207.22.5

IP Address24.88.15.22

Port 80 Port 31337

Segment No. Segment No.

Token Ring

Data Link Layer

Token RingPhys. Layer

Policy

No outside Web access.

Outside connections to Public Web Server Only.

Prevent Web-Radios from eating up the available bandwidth.

Prevent your network from being used for a Smuft DoS attack.

Prevent your network from being tracerouted or scanned.

Firewall Setting

Drop all outgoing packets to any IP, Port 80

Drop all incoming TCP SYN packets to any IP except 130:207:244.203, port 80

Drop all incoming UDP packets - except DNS and Router Broadcasts.

Drop all ICMP packets going to a “broadcast” address (130.207.255.255 or 130.207.0.0).

Drop all incoming ICMP, UDP, or TCP echo-request packets, drop all packets with TTL < 5.

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From "PGP Freeware for MacOS, User's Guide" Version 6.5, Network Associates, Inc., www.pgp.com

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PGP (Pretty Good Privacy) -> GPG

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Access Control

Today almost all systems are protected only by a simple password that is typed in, or sent over a network in the clear.Techniques for guessing passwords:

1. Try default passwords.2. Try all short words, 1 to 3 characters long.3. Try all the words in an electronic dictionary(60,000).4. Collect information about the user’s hobbies, family names, birthday, etc.5. Try user’s phone number, social security number, street address, etc.6. Try all license plate numbers (123XYZ).

Prevention: Enforce good password selection (c0p31an6)

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Kerberos