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computer network

two or more computers connected together via software and hardware so they can communicate

nodes

devices connected to a network

router

enables you to share broadband internet connections

peer-to-peer network

the most common example of a locally administered network

client/server network

the most common type of centrally administered network

peer-to-peer

in this type of network, each node connected to the network can communicate directly with every other node on the network, rather than having a separate device exercise central control over the entire network

client/server network

most networks that have 10 or more nodes

client

in a client/server network, the computer on which users accomplish specific tasks and make specific requests

server

in a client/server network, the computer that provides information or resources to the client computers on the network

server

on a client/server network, provides central control for functions on the network

local area network

networks in which the nodes are located within a small geographic area

wide area network

made up of LANs connected over long distances

transmission media

connect network nodes to each other and to the network

transmission medium

establishes a communications channel between the nodes on a network and can take several forms

data transfer rate

the maximum speed at which data can be transmitted between two nodes on a network

bandwidth

another name for data transfer rate

throughput

the actual speed of data transfer that is achieved; this is usually less than the data transfer rate

network adapters

devices connected to or installed in network nodes that enable the nodes to communicate with each other and to access the network

network interface cards

network adapters that are installed inside computers and peripherals as expansion cards

packets

bunndles in which data is sent over through transmission media

routers and switches

two most common specialized navigation devices

router

transfer packets of data between two or more networks

router

required to send data between the two networks

switches

receive data packets and send them to the node for which they are intended on the same network

networking operating system

client/server networks are controlled by a central server that handles requests for information, Internet access, and the use of peripherals for the rest of the network nodes

ethernet networks

use the Ethernet protocol as the means by which the nodes on the network communicate

ethernet network

requires that you install or attach network adapters to each computer or peripheral you want to connect to the network

unshielded twisted pair cable

most popular transmission medium for wired Ethernet networks

unshielded twisted pair cable

composed of four pairs of wires that are twisted around each other to reduce electrical interference

switch

in an Ethernet network, acts like a traffic signal by enforcing the rules of the data road on the transmission media

switch

in an Ethernet network, acts like a traffic signal by enforcing the rules of the data road on the transmission media

routers

devices that transfer packets of data between two or more networks

wireless network

uses radio waves instead of wires or cables as its transmission media

Wi-Fi

current wireless networks in the United States based on the 802.11 standard

transceiver

a device that translates the electronic data that needs to be sent along the network into radio waves and then broadcasts these radio waves to other network nodes

transceiver

receive signals from other network nodes

wireless access point

a device added to a network to extend the range of the wireless network. It must connect directly to either a switch, a router, or a node on the network

power-line networks

use the existing electrical wiring in your home to connect the nodes in the network

cybercrime

formally defined as any criminal action perpetrated primarily through the use of a computer

cybercriminals

individuals who use computers, networks, and the Internet to perpetrate crime

hacker

as anyone who breaks into a computer system (whether an individual computer or a network) unlawfully

white-hat hackers

hackers who break into systems just for the challenge of it (and who don't wish to steal or wreak havoc on the systems)

white-hat hackers

tout themselves as experts who are performing a needed service for society by helping companies realize the vulnerabilities that exist in their systems

black-hat hackers

hackers who use their knowledge to destroy information or for illegal gain

script kiddies

amateur hackers who use tools created by skilled hackers

packet sniffer

a program that looks at each packet as it travels on the Internet

identity theft

a thief steals your name, address, social security number, and/or bank account and credit card information

trojan horse

a program that appears to be something useful or desirable (like a game or a screen saver) but at the same time does something malicious in the background without your knowledge

backdoor programs

allow hackers to take almost complete control of your computer without your knowledge; hackers can access and delete all files on your computer, send e-mail, run programs, and do just about anything else you can do with your computer

zombies

refers to computers that hackers have control over

denial of service attack

legitimate users are denied access to a computer system because a hacker is repeatedly making requests of that computer system through a computer he or she has taken over as a zombie

distributed denial of service attacks

coordinated attacks launched by hackers from hundreds or thousands of zombies at once

internet connection

the most likely method hackers use to access a computer indirectly

logical ports

virtual communications gateways that allow a computer to organize requests for information from other networks or computers

firewalls

software programs or hardware devices designed to keep computers safe from hackers

virus

a computer program that attaches itself to another computer program (known as the host program) and attempts to spread itself to other computers when files are exchanged

virus

the main purpose is to replicate itself and copy its code into as many other files as possible

boot-sector viruses

viruses that replicate themselves into the hard drive's Master Boot Record

Master Boot Record

a program that executes whenever a computer boots up, ensuring that the virus is loaded immediately

boot-sector virus

viruses that are often transmitted by a floppy disk left in a floppy drive or a flash drive left in a USB port

logic bombs

viruses that are triggered when certain logical conditions are met (such as opening a file)

time bombs

viruses that are triggered by the passage of time or on a certain date

worms

viruses that attempt to travel between systems through networks to spread their infections

scripts

mini programs that are often used to perform legitimate functions on Web sites

macro viruses

viruses that are attached to documents (such as Word files) that use macros

macro

a short series of commands that usually automates repetitive tasks

e-mail viruses

viruses that use the address book in the victim's e-mail system to distribute a virus

encryption viruses

viruses that search for common data files and then compress them using a complex encryption key. The user then has to pay to get the files unlocked

polymorphic viruses

viruses that change their code (or periodically rewrite themselves) to avoid detection

multipartite viruses

viruses that are designed to infect multiple file types in an effort to fool the antivirus software that is looking for them

stealth viruses

viruses that temporarily erase their code from the files where they reside and hide in the active memory of the computer. This helps them avoid detection if only the hard drive is searched for viruses

antivirus software

best defense against viruses

antivirus software

specifically designed to detect viruses and protect your computer and files from harm

virus signatures

are portions of the virus code that are unique to that particular computer virus

antivirus software

scans files for signatures and thereby identifies infected files and the type of virus that is infecting them

quaranteening

the choice of deleting or repairing the infected file and places the virus in a secure area

inoculating

an antivirus program records key attributes about files and re-checks these statistics during a scan

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