1. NETWORKS, COMMUNICATIONS, & SAFEGUARDS4
Chapter

2. Chapter Topics 6.1 From the Analog to the Digital Age 6.2 Networks
Cyberthreats, Hackers, & Safeguards

3. 6.1 From the Analog to the Digital Age

4. Digital Analog Computers use digital signals—0s and 1s, off and on.
All the data that a computer processes is a series of
0s and 1s.
Each signal is a bit.
Analog
But most phenomena in life are analog.
Analog signals use wave variations.
Sound, light, and temperature are analog forms.
Traditional TV and radio use analog signals.
Humans’ vision operates in analog mode.
But analog data can be converted into digital form. Even though digital data is not as exact as analog data, it is easier to manipulate.

5. For data transmission over telephone lines and cables, modems are needed to convert analog data into digital data that computers can use.
Modem is short for modulate/demodulate. Modems modulate (convert) a computer’s digital data to analog data, transmit it, then demodulate (reconvert) it back to digital data for the receiving computer.

7. Converting Reality to Digital Form:
Tape recorders, voices, and musical instruments are analog; CDs are digital
To burn a CD, the digital recording equipment must convert from analog to digital

8. 6.2 Networks

9. A network is a system of interconnected computers, telephones, and/or other communications devices that can communicate with one another and share data
Benefits of Networks
Share peripheral devices, such as printers,
scanners, disk drives
Share programs and data
Better communications, including
Access to shared databases

10. Some disadvantages of networks:
Expense: The initial set up cost of a computer network can be high depending on the number of computers to be connected and the number of connecting devices and NICs .
Security Issues: If a computer is on a network, a computer hacker can get unauthorized access by using different tools.
Rapid Spread of Computer Viruses: If any computer system in a network gets affected by computer virus, there is a possible threat of other systems getting affected, too.
Dependency on the Main File Server: If the main file server of a computer network breaks down, the entire system can become useless.

11. Main types of networks
A wide area network (WAN) is a communications network that covers a wide geographic area, such as a country or the world. The best example of a WAN is the Internet.
A metropolitan area network (MAN) is a communications network covering a city or a suburb. Many cellphone systems are MANs.
A local area network (LAN) connects computers and devices in a limited geographic area, such as one office, one building, or a group of buildings close together. Philadelphia network is an example of LAN.
(continued)

13. How Networks Are Structured:
1. Client/Server
Consists of clients, which are computers that request data, and servers, which are computers that supply data.
2. Peer-to-Peer (P2P)
All computers on the network are “equal” and communicate directly with one another, without relying on servers

15. Intranets & Extranets: use the Internet as their base
Intranets—use infrastructure and standards of the Internet and the web, but for an organization’s internal use only
Extranets—similar to intranets but allows use by selected outside entities, such as suppliers

16. Network linking devices:
Switch— A device that connects computers to a network; sends data only to intended recipients
Bridge—Interface device that connects same type of networks
Gateway—Interface device that connects dissimilar networks
Router—Device that directs messages among several networks, wired and/or wireless
Backbone—Main Internet highway that connects all networks in an organization; includes switches, gateways, routers, etc.

17. Network topologies: Bus, Ring, Star, Mesh
Bus – all nodes are connected to a single wire or cable
Ring – all nodes are connected in a continuous loop
Star – all nodes are connected through a central host
Mesh – messages sent to the destination can take any possible shortest, easiest route to reach its destination. There must be at least two paths to any individual computer to create a mesh network. (Wireless networks are often implemented as a mesh, and the Internet is a mesh.)

18. Bus Network

19. Ring Network

20. Star Network

21. Ethernet
The Ethernet communications protocol is embedded in software and hardware devices intended for building a local area network (LAN), and it is commonly used in star topologies.

22. 6.3 Cyberthreats, Hackers, & Safeguards

23. Problem: Internet was begun to foster collaboration among universities and scientists. They trusted one another. No security was built into the Internet.
Problem: The Internet is open-access and is used by criminals who take advantage of the lack of built-in safeguards.
Problem: Most people connect to the Internet and use their computers in LANs. All it takes is one computer on a LAN that has been compromised for all computers on it to be vulnerable to malware and other threats.

24. Cyberthreats Denial of Service Attacks Viruses
Consist of making repeated requests of a computer or network device, thereby overloading it and denying access to legitimate users
Used to target particular companies or individuals
Viruses
Deviant program that hides in a file or a program on a disk, flash memory drive, in an , or in a web link that causes unexpected effects such as destroying or corrupting data

25. Cyberthreats (continued)
Trojan Horses
Programs that pretend to be a useful program such as a free game or a screensaver but that carry viruses or malicious instructions that damage your computer or install a backdoor or spyware
Backdoors and spyware allow others to access your computer without your knowledge
Worms
A program that copies itself repeatedly into a computer’s memory or disk drive
May copy itself so much it crashes the infected computer

26. Cyberthreats (continued)
How they spread
Via attachments
By infected disks and flash drives
By clicking on infiltrated websites
By downloading infected files from websites
From one infected PC on a LAN to another

27. Cybervillains Hackers are either
Computer people who enjoy learning about programming and computers
People who gain unauthorized access to computers or networks, often for fun or just to see if they can

28. Online Safety Use antivirus software, and keep it current
Install a firewall to monitor network traffic and filter out undesirable types of traffic and undesirable sites
Don’t use the same password for multiple sites
Don’t give out any password information
Use robust passwords:
Minimum 8 characters with letters, numbers, characters
4cats is not a good password; is safer

29. Online Safety (continued)
Install antispyware software
Back up your data, so if your PC is attacked and must be reformatted, you can restore your data
Never download from a website you don’t trust
Consider biometric authentication

30. Online Safety (continued)
Biometrics: science of measuring individual body characteristics
Used in security devices
Examples; hands, fingerprints, iris recognition, face recognition, voice recognition
Now available on laptops