Fetch-Execute Cycle 

The fetch-execute cycle is for any sort of process in a computer, and goes as follows.

• Transfer the contents of the Program Counter to Memory Address Register (MAR)

• Increment the program counter

• Activate Read Line (transfers instruction to data register)

• Transfer contents of data register to instruction register to decode

• Decode the instruction

• Execute the instruction

Firewall  

The firewall is a program that monitors traffic being sent by the computer and traffic being received by the computer to make sure the file doesn’t contain harmful files.

Encryption  

Encryption is a method of protecting data by scrambling it up using public and private keys

Public Key 

The public key is visible to everyone 

Private Key 

The private key is only visible to the owner

The public key can be received from a server host to encrypt data to be sent off back to them, which they can then decrypt using their private key. This can also be done the other way round.

Digital Signature - 

• Used to verify the authenticity of a message sent by a user

• Uses public-private key encryption

• Private key is used to create the signature, which is attached to the message and sent off to the other user

• Receiving user uses the sender’s public key to decrypt the signature to prove that it’s authentic

• If the message has been tampered with the signature will be wrong

• Nearly impossible to accurately forge a digital signature, due to needing the private key

Cache  

L1 Cache - 

Level 1 Cache (L1) is the easiest-to-access cache storage, being stored directly on the processor chip, however has a small storage capacity meaning less data can be stored on it

L2 Cache - 

Level 2 Cache (L2) is a larger piece of cache storage off the chip, which although slower to access than L1 cache, is both quicker to access than RAM and can store more data than L1

Cache Hit - 

Cache hit is when the processor goes to cache to find a piece of data and finds it successfully

Cache Miss -  

Cache miss is when the processor goes to cache to find a piece of data, but cannot find it so has to go further out into RAM or backing storage, taking up more time

Threading  

Threads - 

Are contained within cores which can be given commands, meaning 1 core can do multiple jobs at once. Hyper-threading gives you quicker processing times but is more expensive

Improving Performance  

• Widening the data bus allows for more data to be transferred in a given cycle

• Widening the address bus does NOTHING to improve performance

• Overclocking the processor (more cycles per second) can increase the amount of work done by the processor in a given time, increasing performance

• Increasing cache size means more data can be stored closer to the processor, lessening the chance of a cache miss

• Having more cores can increase the amount of data processed in a cycle

Cyberattacks  

DOS attacks - Denial of service attacks has the intent to “deny service to the site”. There are different types of attacks of which can include: 

• Bandwidth consumption: overloading the bandwidth of the network connection

• Resource starvation: causing so many processes to run that systems become starved of memory, processor time

• DNS attacks: exploits the domain name service (DNS). floods the server with small data packets, causing resource starvation which will deny users access to a website. 

Reasons for DOS attacks - personal, financial, or political reasons

Symptoms of DOS attacks - Inability to access system, incredibly slow performance. (can result in lost revenue and unexpected costs required to resolve the attack)

Floating Point Rep 

Binary File Size Conversions

Anything past terabytes is not required knowledge

Laws

Copyrights, Designs and Patents Act

• Do not shorten the name, must write in full.

• For taking credit for someone else's work.

• For having something that doesn't belong to you

Penalties if broken 

• Up to 10 years in prison.

Computer Misuse Act

• Covers hacking and spreading viruses.

• Viruses are only illegal if used.

• Makes it illegal to gain access to a system w/o permission (hacking.)

Penalties if broken

• Up to 5 years in prison.

• Unlimited fines.

• Banned from technology for life.

Communications Act

• Covers all digital communications.

• Makes cyber terrorism illegal (introducing viruses to vulnerable networks.)

• Makes it illegal to send inappropriate videos/photos w/o permission. (pornography)

GDPR (General Data Protection Regulation)

• Regulates what companies can do with a person's data.

• Gives a person control of their data.

• Companies need to justify what they do with a person's data.

• People must be told what data is being used and how.

• Data must be kept up-to-date.

Penalties if broken

• 5-10 years in prison.

• Fines of up to £500,000.

RIPA (Regulation of Investigatory Powers Act)

• Legal act which requires businesses to inform you when you/your data is being recorded.

• Before recording your data they must have the necessary recording equipment to  ensure that it is kept secure.

• Must give access to law enforcement agencies when required.