Computer Systems Flashcards
Describe the 4 stages of the fetch execute cycle
- The processor sets up the address bus with the required memory location.
- Read line is activated on the control bus. (by the processor)
- An Instruction is fetched from the memory location using the data bus and stored in the instruction register.
- The instruction in the instruction register is decoded/executed.
Explain Unauthorised Access to computer material. (Computer Misuse Act 1999)
Have you ever found, guessed or used someone else’s’ password to log onto their user area? If you do this and then look at their files, even if you don’t change, delete or damage anything, you are still guilty of accessing materials without authorisation - and this is illegal.
(This offence carries the risk of being sentenced to six months in prison and/or a hefty fine.)
Unauthorised access with intent to commit or facilitate a crime. (Computer Misuse Act 1999)
The difference between this and the first offence is that the person gaining access to someone elses’ system is doing so with the sole purpose of doing something illegal.
This might mean that they had to guess or steal the password in order to get into someone’s user area or their bank account. They could do this by trial and error or by using special programs such as spyware or keylogging software, or they could use a relatively new technique called ‘phishing’.
They might want to steal some company secrets or they might want to transfer some money out of your bank account into their own.
(Anyone caught doing this risks up to a five year prison sentence and/or a hefty fine.)
Unauthorised modification of computer material. (Computer Misuse Act 1999)
Everyone deletes files from their own system, maybe they no longer need them or maybe they delete them by mistake. This is fine - there was no intent to cause any damage.
This offence relates to the deletion or changes made to files with the intent to cause damage to an individual or company. The difference is ‘the intent to cause damage’.
This offence also covers purposely introducing viruses to other peoples’ systems.
If you knowingly transmit a virus to others, you are guilty under this section of the Computer Misuse Act.
(This offence carries a penalty of up to five years in prison and/or a fine.)
Making, supplying or obtaining anything which can be used in computer misuse offences.
Making
This includes the writing or creation of computer viruses, worms, trojans, malware, malicious scripts etc.
Supplying
This part covers the distribution of any of the above material whether you have created it yourself or obtained it from elsewhere. It is an offense to supply or distribute these files to others.
Obtaining
If you purposely obtain malicious files such as as computer viruses or scripts that you know could be used to damage computer systems then you have committed an offence under the Computer Misuse Act.
Describe the memory READ operation.
- The processor sets up the address bus with the address of the required memory location.
- The processor activates the READ line on the control bus.
- The contents of the memory location are transferred along the data bus into the processor.
- The instruction is decoded and executed.
Describe the memory WRITE operation.
- The processor sets up the address bus with the address of the required memory location.
- The processor sets up the data bus with the data to be written to memory.
- The processor activates the WRITE line on the control bus.
- The data is transferred along the data bus to the memory location.
What is a Digital Signature?
A digital signature is a way to ensure that an electronic message or document is authentic.
The signature is created when the message is sent, using a private encryption key, opposite to normal PKE.
The signature is then paired with a public key and sent with the message.
When the message run through the public key the result should match the signature.
If they don’t match then the message has been altered en route, so the message has been intercepted and compromised.
What is a Digital Certificate?
Digital Certificates are the attachment to an electronic message used for security purposes.
It is used to verify that a user sending a message is who they claim to be and to bind their public key to them.
Certificates can only be issued by certain trusted entities including Google, Symantec, and Comodo.
The “lock” icon in your browser shows the status of the certificate.
The lock indicates that the website is backed by a digital certificate and is a genuine website and is not a fake set up by criminals
Have you ever found, guessed or used someone else’s’ password to log onto their user area? If you do this and then look at their files, even if you don’t change, delete or damage anything, you are still guilty of accessing materials without authorisation - and this is illegal.
(This offence carries the risk of being sentenced to six months in prison and/or a hefty fine.)
NAME
Explain Unauthorised Access to computer material. (Computer Misuse Act 1999)
The difference between this and the first offence is that the person gaining access to someone elses’ system is doing so with the sole purpose of doing something illegal.
This might mean that they had to guess or steal the password in order to get into someone’s user area or their bank account. They could do this by trial and error or by using special programs such as spyware or keylogging software, or they could use a relatively new technique called ‘phishing’.
They might want to steal some company secrets or they might want to transfer some money out of your bank account into their own.
(Anyone caught doing this risks up to a five year prison sentence and/or a hefty fine.)
NAME
Unauthorised access with intent to commit or facilitate a crime. (Computer Misuse Act 1999)
Everyone deletes files from their own system, maybe they no longer need them or maybe they delete them by mistake. This is fine - there was no intent to cause any damage.
This offence relates to the deletion or changes made to files with the intent to cause damage to an individual or company. The difference is ‘the intent to cause damage’.
This offence also covers purposely introducing viruses to other peoples’ systems.
If you knowingly transmit a virus to others, you are guilty under this section of the Computer Misuse Act.
(This offence carries a penalty of up to five years in prison and/or a fine.)
NAME
Unauthorised modification of computer material. (Computer Misuse Act 1999)
Making
This includes the writing or creation of computer viruses, worms, trojans, malware, malicious scripts etc.
Supplying
This part covers the distribution of any of the above material whether you have created it yourself or obtained it from elsewhere. It is an offense to supply or distribute these files to others.
Obtaining
If you purposely obtain malicious files such as as computer viruses or scripts that you know could be used to damage computer systems then you have committed an offence under the Computer Misuse Act.
NAME
Making, supplying or obtaining anything which can be used in computer misuse offences.
- The processor sets up the address bus with the required memory location.
- Read line is activated on the control bus. (by the processor)
- An Instruction is fetched from the memory location using the data bus and stored in the instruction register.
- The instruction in the instruction register is decoded/executed.
Describe the 4 stages of the fetch execute cycle
- The processor sets up the address bus with the address of the required memory location.
- The processor activates the READ line on the control bus.
- The contents of the memory location are transferred along the data bus into the processor.
- The instruction is decoded and executed.
Describe the memory READ operation.
