GCSE paper Qs Flashcards
Why must sound be converted into a digital format?
Computer systems use binary/ones and zeros/voltage on or off;
Sound is analogue/continuous/wave;
Computers use discrete values;
Describe blagging, phishing and shouldering?
- blagging = victim tricked into giving details
- phishing = victim receives communication from an unknown source - but is a fraud
- watches someone enter their password
How can you prevent infections from malware and the damage caused by malware?
– Pen testing. To allow the organisation to understand where weaknesses may be, in order to strengthen their
system security
- Regularly back up data so that you can restore data that has been accidentally deleted or destroyed
and test backups.
- Ensure software is up to date. = Make sure all software is up to date and patched to prevent any exploitation of known vulnerabilities.
- Anti-virus/ Anti malware is up to date. Ensure anti-virus automatically updates so that the latest vulnerabilities are detected and dealt with.
- Manage the use of privileged accounts and access levels to files. - Controlling the access to files should act as an internal firewall\barrier to prevent unauthorised
access or execution of programs.
- Use network filtering or a firewall. = Prevent\block access into and out of the network using filtering and firewall to stop any malicious communications or transfer of viruses.
- MAC address filtering. Can prevent access by unauthorised devices.
- User training. To educate staff on the dangers of social engineering techniques and other unsafe practices.
How is an image represented in a bitmap?
- Image is divided into pixels
- Each possible colour is represented by a (unique) bit pattern
- The colour of each pixel is stored
- The order of the bit patterns for the individual pixels indicates where the pixel will appear in the image
- Metadata about the image will also be stored
Compare the similarities and differences between trojans, adware, spyware and viruses? How would you reduce the risks from these malwares?
- these are all harmful malware that gives the hacker access to unauthorized data
- Users sometimes choose to allow/install adware (this is not the case with the other types of malware
- Spyware tracks what a user is doing - not adware
- Adware does not do any harm to a computer system (unlike spyware, viruses and Trojans) though it can be irritating and be used to conceal spyware;
- Viruses can replicate themselves / spread without the user being involved;
- Trojans and viruses can be very destructive;
- Spyware and adware work in the same way;
Reduce risk by:
- Install anti-spyware/virus software and keep it updated regularly
- only download things from trusted sources - research it
- don’t use random external devices such as USBs
- Don’t open attachments on emails from people you don’t know/trust;
Does hexadecimal take up more space?
- no as it will be converted to binary
- thus will take the same amount of space
How does a firewall provide network security?
- monitors network traffic and prevents unauthorised access
- opens and closes ports
Explain the difference between these two types of penetration testing
Black
- external hacker so doesn’t know how the system works
- finds loopholes and vulnerabilities
- testing overall weakness in system
White
- internal as insider and knowledge about the system
- given a certain amount of access
- testing certain and specific parts of the system
Describe different categories of malware:
- Trojan (horse); a program that misleads the user into thinking it is another piece of software which, when run, executes another program;
- Spyware; a program that records data such as usernames and passwords on a host system and forwards the information to a third party;
- Worm; code which will run autonomously and replicates itself on a host system
- Ransomware; a program that encrypts user’s data to make it unreadable until they pay for the key;
- Rootkit; malware that has managed to gain ‘root’ admin privileges; = changes permissions in OS
- Adware; code embedded or attached to program files that will persistently show adverts (that attempt to generate revenue);
What is a pixel?
- single point in a graphical image
Why is hexadecimal used?
- hexadecimal is easier (for humans) to read (than binary); A. easier to
understand
• numbers are displayed in a more compact way (in hexadecimal than in
binary);
• it is quicker to type in (hexadecimal numbers than binary numbers);
• it reduces the risk of typing errors (hexadecimal numbers than binary
numbers)
How is analogue sound converted into digital sound?
- a microphone/sound sensor picks up/detects the sound wave;
- this wave is converted to an (electrical) analogue signal;
- the amplitude/height of the wave is measured;
- the sampling takes place at regular intervals;
- these samples are stored as binary values;
Why do we compress things?
To speed up file transfer;
• To use less storage (capacity);
• (It could) save money if you use less bandwidth;
• To use less memory;
• (It could) save money if you use less storage capacity;
How does RLE work?
• the number of consecutive pixels/data points/characters of the same
- colour/value/character would need to be counted;
• (pairs of values would be stored), which would consist of a run length and the colour/value/character of the pixels/data points/text in the run
- add example
Find the errors:
“I would count the number of times each character appears in the string and create a frequency table sorted alphabetically. For example, the letter S has the highest frequency in Figure 2. Next I would take the two characters with the largest frequencies and combine them into a new node. The new node would be added to the end of the frequency table. The two characters with the lowest remaining frequencies are now combined into a new node and the process is repeated until all the characters have been added to nodes and the tree created.
• the characters with the highest frequencies should not be combined // the
characters with the lowest frequencies should be combined;
• the frequency table should not be sorted alphabetically // the frequency table
should be sorted in order of frequency;
• the letter S does not have the highest frequency in Figure 2 // E has the
highest frequency;
• the new node should not be added to the end of the frequency table // the new
node should be inserted in the correct place based on the combined
frequencies;
