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AQA-7517-2-COMPUTER SCIENCE FINAL MARK SCHEME PAPER 2-A LEVEL-Jun2024-v1.0

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AQA-7517-2-COMPUTER SCIENCE FINAL MARK SCHEME PAPER 2-A LEVEL-Jun2024-v1.0 01 All marks AO1 (understanding) Monitoring Firewall could block packets from sources / computers known to be high-risk // could block packets not part of a current communication (stateful inspection); A. firewall could filter/monitor data entering network A. firewall could block packets containing malicious data Proxy server could receive/check downloaded files; Spam filters can block emails from suspicious sources // spam filters can block emails that contain suspicious content // block pop-ups to prevent users clicking on potentially harmful links // have a system that enables the reporting of spam emails // block download of attachments from outside organisation / untrusted sources // block download of attachments based on file type / executables; Web filters can check websites against a list of websites known for having content that might contain/spread a virus; Digital certificates can be used to verify the source of a downloaded file; Digital signature / checksum can be used to verify that a file has not been changed // that a file came from a known source; Protection Enable automatic update of applications / OS to patch code vulnerabilities; A. keep software up to date R. automatic update of anti-virus software Use a virtual machine to execute programs // use a sandbox when executing programs (A. opening files); Set access rights to minimise risk of viruses being able to access / modify sensitive / important data / files; Disable execution of macros in documents (from outside sources); Restrict execution of software from unverified sources // restrict execution of unauthorised software; Encrypt files so that data cannot be extracted from them; Backup data and keep offline / away from computer so it can be recovered; NE. “backup” without explaining that this could be used to recover data or expanding on how backups should be made Disable the use of external drives / removable media; A. disable USB ports Use a computer with the Harvard architecture to prevent data being executed as code; Use a MAC address allow list so that only known devices can join a network; (Enforce) strong passwords / biometric access would make it harder for a hacker to access a computer to install a virus; Code Quality Ensure code does not allow buffer overflow / overrun // ensure code prevents programs writing to memory locations not allocated to them; Test software for security issues / vulnerabilities; Carry out a code review so the code is independently checked by another programmer / other programmers; 4 000006 Page 6 of 35 COMPUTER SCIENCE MARK SCHEME – A-LEVEL COMPUTER SCIENCE – 7517/2 – JUNE 2024 7 Use code analysis software to identify flaws / measure code quality; Only use / load up Internet services / libraries from the Internet if required // use the latest version of libraries // use libraries that are known to have been thoroughly tested // use libraries from trusted sources; Note: Question requires a description. Naming methods eg “backup”, “firewall” without describing how they would be used is not enough to award a mark. Max 4 000007 Page 7 of 35 COMPUTER SCIENCE MARK SCHEME – A-LEVEL COMPUTER SCIENCE – 7517/2 – JUNE 2024 8 Qu Pt Marking guidance Total marks 02 1 All marks AO2 (apply) Award 2 marks for correct answer: 36 (megabytes). A. 4000 x 3000 x log2() ÷ 8 ÷ 1000 ÷ 1000 or equivalent eg 1.5 x log2() If answer is incorrect then award 1 method mark for doing at least three of: • multiplying by 4000 • multiplying by 3000 • multiplying by 24 or 3 • dividing by 1000 • dividing by 1000 a second time • dividing by 8 (do not credit if also multiplied by 3). 2 Qu Pt Marking guidance Total marks 02 2 Mark is AO2 (apply) 7111; A. follow-through of 256 x 1000 ÷ incorrect answer to question part 02.1 if rounded down to nearest whole number 1 Qu Pt Marking guidance Total marks 02 3 All marks AO1 (understanding) (The voltages) are continuously var

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AQA MARK SCHEME



A-level




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COMPUTER SCIENCE




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7517/2




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Paper 2




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Mark scheme
June 2024
Version: 1.0 Final
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Page 1 of 35

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MARK SCHEME – A-LEVEL COMPUTER SCIENCE – 7517/2 – JUNE 2024



Mark schemes are prepared by the Lead Assessment Writer and considered, together with the relevant
questions, by a panel of subject teachers. This mark scheme includes any amendments made at the
standardisation events which all associates participate in and is the scheme which was used by them in
this examination. The standardisation process ensures that the mark scheme covers the students’
responses to questions and that every associate understands and applies it in the same correct way.
As preparation for standardisation each associate analyses a number of students’ scripts. Alternative
answers not already covered by the mark scheme are discussed and legislated for. If, after the
standardisation process, associates encounter unusual answers which have not been raised they are




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required to refer these to the Lead Examiner.

It must be stressed that a mark scheme is a working document, in many cases further developed and




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expanded on the basis of students’ reactions to a particular paper. Assumptions about future mark
schemes on the basis of one year’s document should be avoided; whilst the guiding principles of




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assessment remain constant, details will change, depending on the content of a particular examination
paper.




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No student should be disadvantaged on the basis of their gender identity and/or how they refer to the
gender identity of others in their exam responses.
A consistent use of ‘they/them’ as a singular and pronouns beyond ‘she/her’ or ‘he/him’ will be credited in

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exam responses in line with existing mark scheme criteria.

Further copies of this mark scheme are available from aqa.org.uk
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MARK SCHEME – A-LEVEL COMPUTER SCIENCE – 7517/2 – JUNE 2024



Level of response marking instructions
Level of response mark schemes are broken down into levels, each of which has a descriptor. The
descriptor for the level shows the average performance for the level. There are marks in each level.

Before you apply the mark scheme to a student’s answer read through the answer and annotate it (as
instructed) to show the qualities that are being looked for. You can then apply the mark scheme.




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Step 1 Determine a level




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Start at the lowest level of the mark scheme and use it as a ladder to see whether the answer meets the
descriptor for that level. The descriptor for the level indicates the different qualities that might be seen in
the student’s answer for that level. If it meets the lowest level then go to the next one and decide if it




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meets this level, and so on, until you have a match between the level descriptor and the answer. With
practice and familiarity you will find that for better answers you will be able to quickly skip through the




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lower levels of the mark scheme.

When assigning a level you should look at the overall quality of the answer and not look to pick holes in
small and specific parts of the answer where the student has not performed quite as well as the rest. If

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the answer covers different aspects of different levels of the mark scheme you should use a best fit
approach for defining the level and then use the variability of the response to help decide the mark within
the level, ie if the response is predominantly level 3 with a small amount of level 4 material it would be
placed in level 3 but be awarded a mark near the top of the level because of the level 4 content.

Step 2 Determine a mark
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Once you have assigned a level you need to decide on the mark. The descriptors on how to allocate
marks can help with this. The exemplar materials used during standardisation will help. There will be an
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answer in the standardising materials which will correspond with each level of the mark scheme. This
answer will have been awarded a mark by the Lead Examiner. You can compare the student’s answer
with the example to determine if it is the same standard, better or worse than the example. You can then
use this to allocate a mark for the answer based on the Lead Examiner’s mark on the example.
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You may well need to read back through the answer as you apply the mark scheme to clarify points and
assure yourself that the level and the mark are appropriate.

Indicative content in the mark scheme is provided as a guide for examiners. It is not intended to be
exhaustive and you must credit other valid points. Students do not have to cover all of the points
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mentioned in the Indicative content to reach the highest level of the mark scheme.

An answer which contains nothing of relevance to the question must be awarded no marks.
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MARK SCHEME – A-LEVEL COMPUTER SCIENCE – 7517/2 – JUNE 2024



A-level Computer Science

Paper 2

June 2024




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To Examiners:

• When to award '0' (zero) when inputting marks on CMI+




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A mark of 0 should be awarded where a candidate has attempted a question but failed to
write anything creditworthy.




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Insert a hyphen when a candidate has not attempted a question, so that eventually the
Principal Examiner will be able to distinguish between the two (not attempted / nothing




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creditworthy) in any statistics.

• This mark scheme contains the correct responses which we believe that candidates are
most likely to give. Other valid responses are possible to some questions and should be
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credited. Examiners should refer responses that are not covered by the mark scheme, but
which they deem creditworthy, to a Team Leader.


The following annotation is used in the mark scheme:
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; - means a single mark
// - means alternative response
/ - means an alternative word or sub-phrase
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A. - means acceptable creditworthy answer
R. - means reject answer as not creditworthy
NE. - means not enough
I. - means ignore
DPT. - in some questions a specific error made by a candidate, if repeated, could result in the
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loss of more than one mark. The DPT label indicates that this mistake should only
result in a candidate losing one mark on the first occasion that the error is made.
Provided that the answer remains understandable, subsequent marks should be awarded
as if the error was not being repeated.
TO. - a student has made a valid point, but has then demonstrated that they do not understand the
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point that they have made by including further incorrect or contradictory statements so the
mark should not be awarded.
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