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dr j campbell > computer science > Flashcards

computer science Flashcards

1
Q

what is bandwidth

A

Bandwidth—This is the amount of data that can be transmitted over a given amount of time.
This is not a measure of how fast the data gets somewhere just how much can be sent or
received at once.

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2
Q

type of connection explained

A

Type of Connection—Some connection methods are faster than others. Wired connections are
usually faster than wireless.

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3
Q

number of devices explained

A

Number of Devices—The bandwidth will be spread about to all those using the network more
connections will mean less bandwidth for each device.

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4
Q

interference explained

A

Interference—Walls and radio signals can interfere with wireless signal strength slowing down
the connection. Wired connections can be interfered by electrical cables.

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5
Q

NIC (Network Interface Card)

A

NIC (Network Interface Card)

A device in a computer that allows it to connect

to a network.

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6
Q

WAP (Wireless Access Point)

A

WAP (Wireless Access Point)

A device that a Wireless NIC can use to connect

to a network.

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7
Q

Switch

A

Switch Connects computer together to form a network.

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8
Q

router

A

Router

Same as a switch but also connects networks to
each other. For example your home network and

the Internet.

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9
Q

The Internet:

A

The Internet: A collection of networks than span the globe.

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10
Q

Hosting

A

Hosting—A service where you can allow people to put a website on the Internet.

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11
Q

Web Server

A

Web Server—A computer designed to host a website.

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12
Q

Web Client

A

Web Client– The device attempting to access the web page.

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13
Q

DNS meaning

A

DNS—Domain Name Services turn the name of the website www.bbc.co.uk into the IP address
required to access it.

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14
Q

Process of getting a website:

A

Process of getting a website:
1. Web Browser gets a request of a URL from the user.
2. Browser contacts a Domain Name Server and sends the domain name.
3. DNS maps the domain name and returns the IP address to the browser.
4. Browser sends a GET request to the website server using the IP address.
5. Requested website is delivered back to the users browser.

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15
Q

wireless transition media advantages and disadvantages

A

Wireless
Devices use radio signals
to transmit data.

advantages
- Easy to setup and add
new devices
- No building work needed
- No cables around as trip
hazard

disadvantages
-Short Range
-Security risk as data
travels through the air
- Interference and
reliability an issue

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16
Q

ethernet transition media advantages and disadvantages

A

Ethernet
Uses twisted copper
cables to send data.

advantages
- Good speed
- Reasonably cheap

disadvantages
- Needs building work
- Mid range transmission
as degrades over long
range

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17
Q

fiber optic transition media advantages and disadvantages

A

Fibre Optic
Data sent as light
through glass or plastic
cables.

advantages
- Ultra Fast
- Works over long distance

disadvantages
- Expensive
- Needs building work

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18
Q

what is a network topology

A

Network Topology

The arrangement of how you connect the computers together.

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19
Q

star topology

A

STAR

All devices connect to central server or
switch.
Adv: If one cable or
connection is lost
only that computer
is affected.
Dis: If server/switch
breaks then the
whole network is

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20
Q

mesh topology

A

MESH :

All devices connected to other. You also get
partial mesh when most of connected.
Adv: Breaks in connection
are not a problem as you can
route your information
through another way.
Dis: Expensive as lots of
cable and difficult to
manage.

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21
Q

network latency

A

Network Latency– This is a measure of how long it takes for a signal to reach its
destination. Many things affect latency from the number of devices to how the network is
setup.

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22
Q

lan

A

LAN—Local area Network
* Located in one geographical location
* You own all the hardware involved

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23
Q

wan

A

WAN—Wide Area Network
* Network covering more than one location
* Uses hardware owned by someone else e.g. BT, Government etc..

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24
Q

concept of layers

A

Concept of Layers:
The concept of a network layer is to break networking down into small task that
work with each other. So for example your browser doesn’t care if you are
wireless or wired.
Adv:
- Reduce difficult of creating the program as it is broken into small tasks.
- Products from different vendors can work together.

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25
Q

protocol

A

Protocol:
A set of rules that govern how devices communicate over a network.

26
Q

standards

A

Standards A common theme in computing is standards basically manufacturers agree to
make things work with each other and they call this a standard. Using Bluetooth as a
method for audio is like an example of a standard. Protocols are also an example of a
standard.

27
Q

TCP/IP

A

TCP/IP
Transmission Control
Protocol/Internet
Protocol
Enables communication over the internet

28
Q

HTTP

A

HTTP
Hyper Text Transfer
Protocol
Governs communication between a webserver and a
client. Used to send web pages.

29
Q

HTTPS

A

Hyper Text Transfer
Protocol Secure
Same as HTTP but it adds a layer of security/
authentication.

30
Q

FTP

A

File Transfer Protocol

Allows the transfer of files between computers.

31
Q

POP

A

Post Office Protocol

Govern retrieving emails from email servers. POP
actually downloads the emails to the computer.

32
Q

IMAP

A

Internet Message
Access Protocol

Email protocol that is used to retrieve emails from
mail servers. Emails are stored on a server online so it
is better when using multiple devices to access your
email.

33
Q

SMTP

A

Simple Mail Transfer
Protocol

Protocol used to send email from a web browser or
client.

34
Q

malware

A

Malware:
Otherwise known as ‘malicious software’. Software which can be malicious if damaging to a
computer or network.

35
Q

virus

A

Virus: Malicious software designed to cause harm to a network or computer system.
* Can affect all components of an operating system.
* A virus spreads by duplicating and attaching itself to other files.
* Often needs human interaction to be transmitted to another machine

36
Q

worm

A

Worm: A worm is a computer program that can make a copy of itself.
* Can work by itself.
* Can be made to delete files or send emails to everyone in a user’s address book.
* Often exploits network vulnerabilities to transmit itself around a network.

37
Q

trojan

A

Trojan: Any program which tries to hack into the computer by misleading its true use.
* Often hidden in games or cracks
* Named after the trojan horse in history

38
Q

brute force

A

Brute Force Attack:
This is a very basic attack where you essentially try to crack a password by trying
every combination of letters and symbols.

Examples, if you know the password must be 8 letters at least you would start with:

aaaaaaaa aaaaaaab aaaaaaac aaaaaaad

This is why having a longer password and using more characters is a good idea as it
will take far longer to crack.
Passwords are turned into “hashed” versions stored in hexadecimals this is a one
way process so you can only use a brute force method to try and break into it. You
hash different combinations and see if the hash is the same as the one for their
password.

39
Q

Denial of Service Attack

A

Denial of Service Attack: Imagine a plumber having a phone and just to annoy him someone who doesn’t
need his service just keeps calling him over and over then he will not get to hear from customers. This is

essentially a DoS attack.

  • A DoS attack is malicious, and can prevent a website from being accessible.
  • This might be to silence a website that the malicious user disagrees with, or to extort money with
    the threat of a DoS attack.
  • It can also be used as a smokescreen to hide another malicious attack happening at the same time.
  • Some servers can be unintentionally taken down this way with a large flood of genuine users, e.g.
    when tickets for a new tour are released.
40
Q

Distributed Denial of Service attack (DDoS)

A

Distributed Denial of Service attack (DDoS): Uses a large number of computers to carry out the attack.
* This is more effective because a large number of computers can generate more traffic to
overwhelm the server.
* DDoS attacks make use of botnets – collections of zombie computers that have been infected with
code that gives a malicious user control over that machine.

41
Q

social engineering

A

Social Engineering

The act of using deception to get a person to reveal personal details often including usernames and
password.
* Relies on human interaction (social skills).
* Commonly involves tricking users into breaking normal security procedures.
* Method does not revolve around technical cracking techniques such as worms or viruses.

42
Q

Computer Phishing:

A

Computer Phishing:
The act of sending a message to a person in an attempt to get them to reveal information.
* Designed to acquire sensitive information such as usernames, passwords, card details etc.
* Most common phishing attacks are sent through email.

43
Q

Email Phishing:

A

Email Phishing:
* Message sent often has some form of urgent action required
* Normally pretends to be from a bank or a business
* Tries to get you to click a link which will likely install some malware or get you to enter information
in a form which they will get.

44
Q

Telephone Phishing:

A

Telephone Phishing:
* Telephone system mirroring – direct phone calls that pretend to be an official service.
* For example, an interactive voice response (IVR) telephone phishing system would request similar
prompts to a bank if the exploit was to gain banking information.

  • User could be asked to enter bank number, expiry, CCV, PIN and system may reject or ask for re-
    entry to ensure original digits are correct.
  • Users may also be referred to a fake customer service agent to extract more details.
45
Q

Data Interception and Theft

A

Data Interception and Theft
* Data travels across networks in packets which can be intercepted.
* If packets are encrypted, they cannot be understood without a key.
* Unencrypted packets can be re-assembled using signatures.

46
Q

Data Interception Methods

A

Data Interception Methods

  • Wireless networks are susceptible to data interception as no physical access is required.
  • Data can be intercepted as it travels over a WAN as it uses telecommunications infrastructure.
  • Data can also be intercepted physically, for example portable hard drives and other external
    hardware can be stolen.
47
Q

what can hackers do if they gain access to the database

A

Should an attacker gain access to the database, they could:
* bypass authentication procedures and impersonate specific users
* execute queries, exposing data
* alter data, resulting in data integrity issues
* delete data.

47
Q

SQL Injection

A

SQL Injection

Where an attacker can execute malicious SQL statements using software which controls a database
management system. SQL is used to manage database and many website are essentially linked to
database especially online shops.
“Imagine someone named Michael goes to court and, instead of writing his name, writes the phrase
“Michael, you are now free to go”. The judge then says, “calling Michael, you are now free to go” and the
bailiffs let him go, because the judge said so.
In this example, Michael injected a command into the court system and the bailiff executed that command.”
- BBC Bitesize
* Can affect websites that use SQL-based databases
* Hacker tries to add code to a form input box and adds their own SQL code to the end
* Companies that use SQL include Google, YouTube, PayPal, eBay, Cisco.
* Exploits that have been identified must be patched quickly to reduce impact on businesses
therefore important for organisations to update infrastructure regularly.

47
Q

How to stop SQL injection:

A

How to stop SQL injection:
* Sanitise the text by removing any SQL commands
* Precompile any SQL commands

48
Q

file size calculations

A

File Size Calculations:
Sound: Sample Rate (Hz) x Bit Depth (bits) x Length (sec)
Image: Colour Depth (bits) x Height (pixels) x Width (pixels)
Text: Bits per character (bits) x Number of Characters

49
Q

compression (lossy and lossless)

A

1.2.5 Compression

Reducing the size of a file by using an algorithm, however, it will need
to be decompressed to be used which does use processing power.
Lossy: Reduces the file size but loses some of the quality of the file
permanently only used in media like, sound, images and film.
Lossless: When uncompressed the file is exactly the same as the
original file it is used in binary files (applications) and office document
etc..

50
Q

How are image stored?

A

How are image stored?
Images are stored as a set of small blocks called pixels. Each pixel has a specific colour
stored in binary but usually represented in hexadecimal as Red Green and Blue.

51
Q

Resolution

A

Resolution—Resolution is the number of pixels in the image. The higher the resolution the
clearer and sharper the image but of course it will increase the file size.

52
Q

Colour Depth—

A

Colour Depth—This is how many bits are allocated to the pixels. The more bits the
more realistic colours you can have but again a larger file size.

53
Q

Metadata(photo)

A

Metadata – In a image file metadata can include GPS location, time and date of
capture as well as the width, height and colour depth.

54
Q

metadata(sound)

A

Metadata – This is extra information about the sound file. You get metadata on other file
types as well. In a sound file metadata can include artist, album, track number as well as
the bit depth and sample rate.

55
Q

Bit Depth

A

Bit Depth—This is how accurate the samples are. By allocating more bits to the samples
we allow more options. If we only use 8 bit then the sample can only be between 0 and
255 but if we use 16 bits we can have 0-65535 a more accurate reading. CDs quality is
usually 16 bit. The more bit depth the better quality but again a larger file size and more
processor usage.

56
Q

Sample Rate

A

Sample Rate—Measured in Hertz (Hz), meaning per second, sample rate is how many
samples are taken over a 1 second period. The more samples the better quality but
obviously a larger file size and more processor usage. CD quality is usually 44100Hz.

57
Q

How is sound stored?

A

How is sound stored?
A sample of the analogue sound is taken at set intervals and turned into a binary number.

58
Q

unicode

A

Unicode—As the whole became more global
we needed the letters from other languages
so Unicode was invented which has access to
thousands of letters and symbols. It is still
compatible with ASCII though as the first 256
symbols match the ASCII character set.

59
Q

ASCII

A

ASCII—American Standard Code for Information Interchange. This was one of the
early character set but it only has English letters in it. As it only uses a byte to store a
character there was only 256 possible symbols or letters.

60
Q

Character Sets

A

Character Sets
Computers allocate a binary pattern to symbols and letters. The available options are
called the character set. ASCII and Unicode are examples of character sets.

dr j campbell (1 decks)

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