computer science Flashcards

Question

protocol

Answer 1

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

Answer 2

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.

Answer 3

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

Answer 4

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

Answer 5

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

Answer 6

File Transfer Protocol Allows the transfer of files between computers.

Answer 7

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

Answer 8

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.

Answer 9

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

Answer 10

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

Answer 11

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

Answer 12

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.

Answer 13

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

Answer 14

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.

Answer 15

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.

Answer 16

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.

Answer 17

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.

Answer 18

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.

Answer 19

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.

Answer 20

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.

Answer 21

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.

Answer 22

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.

Answer 23

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.

Answer 24

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.

Answer 25

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

Answer 26

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

Answer 27

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..

Answer 28

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.

Answer 29

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.

Answer 30

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.

Answer 31

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

Answer 32

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.

Answer 33

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.

Answer 34

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.

Answer 35

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

Answer 36

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.

Answer 37

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.

Answer 38

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.

computer science Flashcards

(62 cards)