Computer Science 0478 | Paper 1 Mock 01 | Computer Systems
Question 1 Report
(a) Explain what an echo check is.
[2]
(b) Describe how an echo check detects errors.
[2]
(c) State one advantage and one disadvantage of using an echo check.
[1]
(a) An echo check is an error detection method where the receiver sends the received data back (echoes it) to the sender [1] so that the sender can compare the echoed data with the original to check for transmission errors [1].
(b) After transmitting data, the sender waits for the receiver to echo back the received data. [1] The sender compares the echoed data with the original. If they differ, an error has occurred during transmission and the data is resent. [1]
(c) Advantage: simple to implement, requiring no complex calculations or algorithms. [1]
Disadvantage: effectively doubles the amount of data transmitted (every piece of data must be sent twice), which halves the effective throughput and is inefficient for large data transfers. The echo itself could also be corrupted during return transmission.
Answer Details
(a) An echo check is an error detection method where the receiver sends the received data back (echoes it) to the sender [1] so that the sender can compare the echoed data with the original to check for transmission errors [1].
(b) After transmitting data, the sender waits for the receiver to echo back the received data. [1] The sender compares the echoed data with the original. If they differ, an error has occurred during transmission and the data is resent. [1]
(c) Advantage: simple to implement, requiring no complex calculations or algorithms. [1]
Disadvantage: effectively doubles the amount of data transmitted (every piece of data must be sent twice), which halves the effective throughput and is inefficient for large data transfers. The echo itself could also be corrupted during return transmission.
Question 2 Report
(a) Explain what a brute force attack is in the context of encryption.
[2]
(b) A symmetric encryption key is 8 bits long. Calculate the number of possible keys.
[1]
(c) Explain why modern encryption uses key lengths of 128 bits or more.
[2]
(d) State two methods other than brute force that an attacker might use to break encryption.
[2]
(e) Explain one measure that can be taken to protect against brute force attacks on login systems.
[1]
(a) A brute force attack is a method of attempting to break encryption by systematically trying every possible key in sequence. [1] The attacker uses software to generate and test each key against the ciphertext until the correct one is found, producing meaningful plaintext. It is essentially a trial-and-error approach that guarantees success given enough time. [1]
(b) An 8-bit key means each bit can be either 0 or 1, giving:
\( 2^8 = 256 \) possible keys [1]
This is a very small key space, meaning a computer could try all 256 keys almost instantly.
(c) Modern encryption uses key lengths of 128 bits or more because this creates an astronomically large key space. A 128-bit key provides \( 2^{128} \approx 3.4 \times 10^{38} \) possible combinations. [1] Even the fastest supercomputers would need billions of years to try every combination, making brute force attacks computationally infeasible. [1]
(d) Two methods other than brute force that attackers might use: [2]
- Social engineering: manipulating or deceiving a person into revealing the encryption key, password, or other sensitive information. [1]
- Dictionary attack: trying a list of commonly used passwords and words rather than every possible combination, exploiting the tendency for people to choose predictable passwords. [1]
(e) One protective measure is account lockout: the system locks the account after a set number of failed login attempts (for example, 5 incorrect passwords). [1] This prevents an attacker from rapidly trying thousands of passwords because the account becomes inaccessible after a few failures.
Answer Details
(a) A brute force attack is a method of attempting to break encryption by systematically trying every possible key in sequence. [1] The attacker uses software to generate and test each key against the ciphertext until the correct one is found, producing meaningful plaintext. It is essentially a trial-and-error approach that guarantees success given enough time. [1]
(b) An 8-bit key means each bit can be either 0 or 1, giving:
\( 2^8 = 256 \) possible keys [1]
This is a very small key space, meaning a computer could try all 256 keys almost instantly.
(c) Modern encryption uses key lengths of 128 bits or more because this creates an astronomically large key space. A 128-bit key provides \( 2^{128} \approx 3.4 \times 10^{38} \) possible combinations. [1] Even the fastest supercomputers would need billions of years to try every combination, making brute force attacks computationally infeasible. [1]
(d) Two methods other than brute force that attackers might use: [2]
- Social engineering: manipulating or deceiving a person into revealing the encryption key, password, or other sensitive information. [1]
- Dictionary attack: trying a list of commonly used passwords and words rather than every possible combination, exploiting the tendency for people to choose predictable passwords. [1]
(e) One protective measure is account lockout: the system locks the account after a set number of failed login attempts (for example, 5 incorrect passwords). [1] This prevents an attacker from rapidly trying thousands of passwords because the account becomes inaccessible after a few failures.
Question 3 Report
A shop database has a table called Products with the following data.
| ProductID | Name | Category | Price | StockLevel |
|---|---|---|---|---|
| 1 | Keyboard | Peripherals | 25.99 | 45 |
| 2 | Mouse | Peripherals | 12.50 | 120 |
| 3 | Monitor | Display | 199.99 | 15 |
| 4 | USB Cable | Accessories | 5.99 | 200 |
| 5 | Headset | Peripherals | 34.99 | 30 |
(a) Write an SQL query to display the Name and Price of all products in the Peripherals category.
[3]
(b) Write an SQL query to find all products where the StockLevel is less than 50.
[2]
(c) Write an SQL query to display all products ordered by Price from highest to lowest.
[2]
This question tests your ability to write SQL queries to retrieve specific data from a database table. [7]
(a) SQL query to display the Name and Price of all Peripherals products: [3]
SELECT Name, Price
FROM Products
WHERE Category = 'Peripherals'This query works as follows:
- SELECT Name, Price specifies which columns to display in the results (only the product name and its price, not all columns). [1]
- FROM Products identifies the table to query. [1]
- WHERE Category = 'Peripherals' filters the results to include only rows where the Category field matches 'Peripherals'. [1]
The query would return:
| Name | Price |
|---|---|
| Keyboard | 25.99 |
| Mouse | 12.50 |
| Headset | 34.99 |
(b) SQL query to find all products with StockLevel less than 50: [2]
SELECT * FROM Products
WHERE StockLevel < 50SELECT * retrieves all columns. The WHERE StockLevel < 50 condition filters to show only products with stock below 50 units. [1] This would return Keyboard (45), Monitor (15), and Headset (30). [1]
(c) SQL query to display all products ordered by Price from highest to lowest: [2]
SELECT * FROM Products
ORDER BY Price DESCORDER BY Price sorts the results by the Price column. [1] DESC specifies descending order (highest to lowest). Without DESC, the default would be ascending (lowest to highest). [1] The results would appear in this order: Monitor (199.99), Headset (34.99), Keyboard (25.99), Mouse (12.50), USB Cable (5.99).
Answer Details
This question tests your ability to write SQL queries to retrieve specific data from a database table. [7]
(a) SQL query to display the Name and Price of all Peripherals products: [3]
SELECT Name, Price
FROM Products
WHERE Category = 'Peripherals'This query works as follows:
- SELECT Name, Price specifies which columns to display in the results (only the product name and its price, not all columns). [1]
- FROM Products identifies the table to query. [1]
- WHERE Category = 'Peripherals' filters the results to include only rows where the Category field matches 'Peripherals'. [1]
The query would return:
| Name | Price |
|---|---|
| Keyboard | 25.99 |
| Mouse | 12.50 |
| Headset | 34.99 |
(b) SQL query to find all products with StockLevel less than 50: [2]
SELECT * FROM Products
WHERE StockLevel < 50SELECT * retrieves all columns. The WHERE StockLevel < 50 condition filters to show only products with stock below 50 units. [1] This would return Keyboard (45), Monitor (15), and Headset (30). [1]
(c) SQL query to display all products ordered by Price from highest to lowest: [2]
SELECT * FROM Products
ORDER BY Price DESCORDER BY Price sorts the results by the Price column. [1] DESC specifies descending order (highest to lowest). Without DESC, the default would be ascending (lowest to highest). [1] The results would appear in this order: Monitor (199.99), Headset (34.99), Keyboard (25.99), Mouse (12.50), USB Cable (5.99).
Question 4 Report
The diagram shows a simplified view of a central processing unit (CPU).
(a) State the purpose of the ALU. [2]
(b) State the purpose of the Control Unit. [2]
(c) State what each of these registers is used for:
(i) Program Counter (PC) [1]
(ii) Memory Address Register (MAR) [1]
(iii) Memory Data Register (MDR) [1]
(iv) Accumulator (ACC) [1]
(a) Purpose of the ALU [2]
The ALU (Arithmetic Logic Unit) performs arithmetic operations such as addition, subtraction, multiplication, and division on numerical data. [1]
It also performs logical operations such as comparisons (AND, OR, NOT) and determining whether values are equal, greater than, or less than each other. These logical comparisons are essential for decision-making in programs (e.g. IF statements). [1]
(b) Purpose of the Control Unit [2]
The Control Unit (CU) controls and coordinates the activities of all other components within the CPU and the wider computer system. [1]
It fetches instructions from memory, decodes them to determine what operation is required, and sends the appropriate control signals to other components (ALU, registers, memory, I/O devices) to execute each instruction in the correct sequence. [1]
(c) Register purposes [4]
(i) Program Counter (PC): Holds the memory address of the next instruction to be fetched and executed. After each fetch, it is incremented (usually by 1) so it points to the following instruction. [1]
(ii) Memory Address Register (MAR): Holds the address of the memory location that is about to be read from or written to. This address is placed on the address bus. [1]
(iii) Memory Data Register (MDR): Holds the data that has been fetched from memory (during a read operation) or the data that is about to be written to memory (during a write operation). It acts as a buffer between the CPU and main memory. [1]
(iv) Accumulator (ACC): Holds the results of calculations and logical operations performed by the ALU. It is the primary working register for arithmetic and serves as a temporary store for intermediate results. [1]
Answer Details
(a) Purpose of the ALU [2]
The ALU (Arithmetic Logic Unit) performs arithmetic operations such as addition, subtraction, multiplication, and division on numerical data. [1]
It also performs logical operations such as comparisons (AND, OR, NOT) and determining whether values are equal, greater than, or less than each other. These logical comparisons are essential for decision-making in programs (e.g. IF statements). [1]
(b) Purpose of the Control Unit [2]
The Control Unit (CU) controls and coordinates the activities of all other components within the CPU and the wider computer system. [1]
It fetches instructions from memory, decodes them to determine what operation is required, and sends the appropriate control signals to other components (ALU, registers, memory, I/O devices) to execute each instruction in the correct sequence. [1]
(c) Register purposes [4]
(i) Program Counter (PC): Holds the memory address of the next instruction to be fetched and executed. After each fetch, it is incremented (usually by 1) so it points to the following instruction. [1]
(ii) Memory Address Register (MAR): Holds the address of the memory location that is about to be read from or written to. This address is placed on the address bus. [1]
(iii) Memory Data Register (MDR): Holds the data that has been fetched from memory (during a read operation) or the data that is about to be written to memory (during a write operation). It acts as a buffer between the CPU and main memory. [1]
(iv) Accumulator (ACC): Holds the results of calculations and logical operations performed by the ALU. It is the primary working register for arithmetic and serves as a temporary store for intermediate results. [1]
Question 5 Report
(a) Explain the difference between firmware and software.
[2]
(b) State one example of firmware.
[1]
(c) Explain why firmware is stored in ROM rather than RAM.
[2]
(d) A computer's BIOS/UEFI is an example of firmware. Describe the role of the BIOS/UEFI during the boot process.
[3]
(a) Firmware is software that is permanently (or semi-permanently) stored in hardware, typically in ROM or flash memory. It controls the fundamental low-level operations of a device and is not routinely changed by the user. [1] Regular software (application or system software) is stored on secondary storage, loaded into RAM when needed, and can be easily installed, updated, or removed by the user at any time. [1]
(b) The BIOS/UEFI in a computer is a common example of firmware. It runs every time the computer is switched on, before the operating system loads. [1]
(c) Firmware is stored in ROM (Read-Only Memory) because ROM is non-volatile, meaning it retains its contents when the power is turned off. [1] This is essential because the firmware must be available immediately when the device is switched on, before the operating system or any other software has loaded from secondary storage. If it were in RAM (which is volatile), it would be lost every time the power was cut. [1]
(d) During the boot process, the BIOS/UEFI performs the following role:
- It carries out a Power-On Self-Test (POST) to check that essential hardware components (CPU, RAM, storage devices) are present and functioning correctly. [1]
- It identifies the boot device (hard drive, SSD, USB, or network) that contains the operating system, following a pre-configured boot order. [1]
- It loads the operating system's boot loader from the boot device into RAM and transfers control to it, which then continues loading the full operating system. [1]
Answer Details
(a) Firmware is software that is permanently (or semi-permanently) stored in hardware, typically in ROM or flash memory. It controls the fundamental low-level operations of a device and is not routinely changed by the user. [1] Regular software (application or system software) is stored on secondary storage, loaded into RAM when needed, and can be easily installed, updated, or removed by the user at any time. [1]
(b) The BIOS/UEFI in a computer is a common example of firmware. It runs every time the computer is switched on, before the operating system loads. [1]
(c) Firmware is stored in ROM (Read-Only Memory) because ROM is non-volatile, meaning it retains its contents when the power is turned off. [1] This is essential because the firmware must be available immediately when the device is switched on, before the operating system or any other software has loaded from secondary storage. If it were in RAM (which is volatile), it would be lost every time the power was cut. [1]
(d) During the boot process, the BIOS/UEFI performs the following role:
- It carries out a Power-On Self-Test (POST) to check that essential hardware components (CPU, RAM, storage devices) are present and functioning correctly. [1]
- It identifies the boot device (hard drive, SSD, USB, or network) that contains the operating system, following a pre-configured boot order. [1]
- It loads the operating system's boot loader from the boot device into RAM and transfers control to it, which then continues loading the full operating system. [1]
Question 6 Report
(a) The diagram shows an analogue sound wave being digitised.
Explain what the black dots on the diagram represent.
[2]
(b) Explain why the digitised version of the sound is not a perfect copy of the original analogue wave.
[2]
(c) Describe two ways the accuracy of the digital recording could be improved.
[2]
(a) Explain what the black dots on the diagram represent. [2]
The black dots are sample points where the amplitude (loudness) of the analogue sound wave has been measured and recorded as a digital value. [1] Each dot captures the height of the wave at one specific moment in time. The analogue-to-digital converter (ADC) takes these measurements at regular intervals determined by the sampling rate. [1]
(b) Explain why the digitised version is not a perfect copy. [2]
The digital recording only captures the wave's amplitude at the discrete sample points, so any changes in the sound between samples are missed entirely. The faster the wave changes, the more detail is lost between samples. [1] Additionally, the amplitude value at each sample is rounded to the nearest level allowed by the bit depth (this is called quantisation). If the true amplitude falls between two available levels, the recorded value is an approximation, introducing a small error called quantisation noise. [1]
(c) Describe two ways the accuracy of the digital recording could be improved. [2]
Way 1: Increase the sampling rate (take more samples per second). This captures the wave at more frequent intervals, so less detail is lost between sample points. The digitised waveform follows the original shape much more closely. [1]
Way 2: Increase the bit depth (use more bits per sample). This provides more amplitude levels to choose from, so each sample value is a closer approximation to the true amplitude. The gap between consecutive levels becomes smaller, reducing quantisation error. [1]
Answer Details
(a) Explain what the black dots on the diagram represent. [2]
The black dots are sample points where the amplitude (loudness) of the analogue sound wave has been measured and recorded as a digital value. [1] Each dot captures the height of the wave at one specific moment in time. The analogue-to-digital converter (ADC) takes these measurements at regular intervals determined by the sampling rate. [1]
(b) Explain why the digitised version is not a perfect copy. [2]
The digital recording only captures the wave's amplitude at the discrete sample points, so any changes in the sound between samples are missed entirely. The faster the wave changes, the more detail is lost between samples. [1] Additionally, the amplitude value at each sample is rounded to the nearest level allowed by the bit depth (this is called quantisation). If the true amplitude falls between two available levels, the recorded value is an approximation, introducing a small error called quantisation noise. [1]
(c) Describe two ways the accuracy of the digital recording could be improved. [2]
Way 1: Increase the sampling rate (take more samples per second). This captures the wave at more frequent intervals, so less detail is lost between sample points. The digitised waveform follows the original shape much more closely. [1]
Way 2: Increase the bit depth (use more bits per sample). This provides more amplitude levels to choose from, so each sample value is a closer approximation to the true amplitude. The gap between consecutive levels becomes smaller, reducing quantisation error. [1]
Question 7 Report
A computer system uses both primary storage and secondary storage.
(a) State two examples of primary storage. [2]
(b) Explain the difference between RAM and ROM. [4]
(c) State two reasons why secondary storage is needed in a computer system. [2]
(a) Two examples of primary storage [2]
- RAM (Random Access Memory) [1]
- ROM (Read Only Memory) [1]
(b) Differences between RAM and ROM [4]
| Feature | RAM | ROM |
|---|---|---|
| Volatility | Volatile: contents are lost when the power is turned off. [1] | Non-volatile: contents are retained permanently, even without power. |
| Purpose | Stores the operating system, applications, and data that are currently in use by the processor. [1] | Stores the boot-up instructions (BIOS/firmware) needed to start the computer and perform initial hardware checks. |
| Read/Write | Contents can be read from and written to by the processor during normal operation. [1] | Contents can normally only be read, not written to during normal use. |
| Typical capacity | Much larger capacity than ROM in a modern computer (e.g. 8-32 GB). [1] | Relatively small capacity (e.g. a few MB), sufficient only for the startup firmware. |
(c) Two reasons why secondary storage is needed [2]
- Secondary storage is non-volatile, so it retains data when the computer is turned off. Without it, all files and programs would be lost every time the computer shuts down, since RAM is volatile. [1]
- Secondary storage provides much larger capacity than primary storage (hundreds of GB to several TB), allowing users to save large volumes of files, applications, and data permanently. [1]
Answer Details
(a) Two examples of primary storage [2]
- RAM (Random Access Memory) [1]
- ROM (Read Only Memory) [1]
(b) Differences between RAM and ROM [4]
| Feature | RAM | ROM |
|---|---|---|
| Volatility | Volatile: contents are lost when the power is turned off. [1] | Non-volatile: contents are retained permanently, even without power. |
| Purpose | Stores the operating system, applications, and data that are currently in use by the processor. [1] | Stores the boot-up instructions (BIOS/firmware) needed to start the computer and perform initial hardware checks. |
| Read/Write | Contents can be read from and written to by the processor during normal operation. [1] | Contents can normally only be read, not written to during normal use. |
| Typical capacity | Much larger capacity than ROM in a modern computer (e.g. 8-32 GB). [1] | Relatively small capacity (e.g. a few MB), sufficient only for the startup firmware. |
(c) Two reasons why secondary storage is needed [2]
- Secondary storage is non-volatile, so it retains data when the computer is turned off. Without it, all files and programs would be lost every time the computer shuts down, since RAM is volatile. [1]
- Secondary storage provides much larger capacity than primary storage (hundreds of GB to several TB), allowing users to save large volumes of files, applications, and data permanently. [1]
Question 8 Report
The table shows different types of cyber threat.
| Threat | Description |
|---|---|
| Pharming | |
| Spyware | |
| Adware | |
| Trojan |
(a) Complete the table by describing each cyber threat. [4]
(b) For each threat in the table, state one method that can be used to protect against it. [4]
(a) Descriptions of each cyber threat [4]
| Threat | Description |
|---|---|
| Pharming | Malicious code (often installed via malware or DNS poisoning) redirects a user from a legitimate website to a convincing fake website without the user's knowledge, even when the correct URL is typed into the browser. The fake site then harvests login credentials or personal data. [1] |
| Spyware | Software that secretly monitors and collects information about a user's activities - such as browsing habits, keystrokes, and login credentials - and sends this data to a third party without the user's consent. [1] |
| Adware | Software that automatically displays or downloads unwanted advertisements on the user's computer, often bundled with free software downloads. While not always directly harmful, it degrades performance and can redirect to malicious sites. [1] |
| Trojan | A program that appears to be legitimate software (e.g. a game or utility) but contains hidden malicious code that executes when the program is run, potentially opening a backdoor for an attacker. [1] |
(b) One protection method for each threat [4]
| Threat | Preventive Measure |
|---|---|
| Pharming | Use up-to-date anti-malware software that can detect and remove pharming code, and always check for HTTPS and a valid security certificate before entering login details on a website. [1] |
| Spyware | Run regular anti-spyware scans using dedicated security software, and avoid downloading programs from untrusted or unverified sources. [1] |
| Adware | Use an ad blocker in the web browser and be cautious when installing free software, checking for bundled programs during the installation process and opting out. [1] |
| Trojan | Only download software from trusted and verified sources (official websites, app stores), and keep anti-virus software up to date so it can detect known Trojan signatures. [1] |
Answer Details
(a) Descriptions of each cyber threat [4]
| Threat | Description |
|---|---|
| Pharming | Malicious code (often installed via malware or DNS poisoning) redirects a user from a legitimate website to a convincing fake website without the user's knowledge, even when the correct URL is typed into the browser. The fake site then harvests login credentials or personal data. [1] |
| Spyware | Software that secretly monitors and collects information about a user's activities - such as browsing habits, keystrokes, and login credentials - and sends this data to a third party without the user's consent. [1] |
| Adware | Software that automatically displays or downloads unwanted advertisements on the user's computer, often bundled with free software downloads. While not always directly harmful, it degrades performance and can redirect to malicious sites. [1] |
| Trojan | A program that appears to be legitimate software (e.g. a game or utility) but contains hidden malicious code that executes when the program is run, potentially opening a backdoor for an attacker. [1] |
(b) One protection method for each threat [4]
| Threat | Preventive Measure |
|---|---|
| Pharming | Use up-to-date anti-malware software that can detect and remove pharming code, and always check for HTTPS and a valid security certificate before entering login details on a website. [1] |
| Spyware | Run regular anti-spyware scans using dedicated security software, and avoid downloading programs from untrusted or unverified sources. [1] |
| Adware | Use an ad blocker in the web browser and be cautious when installing free software, checking for bundled programs during the installation process and opting out. [1] |
| Trojan | Only download software from trusted and verified sources (official websites, app stores), and keep anti-virus software up to date so it can detect known Trojan signatures. [1] |
Question 9 Report
A business uses different methods to verify the identity of customers accessing its online services.
| Verification method | How it works | One limitation |
|---|---|---|
| Knowledge-based questions | ||
| Email verification link | ||
| SMS one-time passcode |
(a) Complete the table by describing how each method works and giving one limitation. [6]
(b) Explain why using a combination of these methods is more secure than using any single method. [2]
(a) How each verification method works and one limitation [6]
| Method | How It Works | One Limitation |
|---|---|---|
| Knowledge-based questions | The user is asked questions about personal information that they should know the answers to, such as their mother's maiden name, their first school, or their childhood pet. [1] | The answers can sometimes be found on social media profiles or public records, or guessed by someone who knows the user personally, making this method vulnerable to social engineering. [1] |
| Email verification link | A unique, time-limited link is sent to the user's registered email address. The user must click the link to confirm their identity and prove they have access to that email account. [1] | If the user's email account has been compromised (e.g. through a phishing attack or password reuse), an attacker could click the verification link and impersonate the user. [1] |
| SMS one-time passcode | A temporary numeric code is sent via SMS to the user's registered mobile phone number. The code must be entered into the website within a short time limit (typically 2-5 minutes) to confirm identity. [1] | The code could be intercepted through SIM swapping (where an attacker convinces the phone provider to transfer the number to a new SIM) or if the phone is stolen. [1] |
(b) Why combining methods is more secure [2]
Using a combination ensures that even if one method is compromised (e.g. a hacker knows the answer to a security question), they still need to bypass additional methods to gain access. [1]
Different methods verify identity using different channels (knowledge, email, phone), reducing the chance that a single attack vector (e.g. phishing) can defeat all of them simultaneously. [1]
Answer Details
(a) How each verification method works and one limitation [6]
| Method | How It Works | One Limitation |
|---|---|---|
| Knowledge-based questions | The user is asked questions about personal information that they should know the answers to, such as their mother's maiden name, their first school, or their childhood pet. [1] | The answers can sometimes be found on social media profiles or public records, or guessed by someone who knows the user personally, making this method vulnerable to social engineering. [1] |
| Email verification link | A unique, time-limited link is sent to the user's registered email address. The user must click the link to confirm their identity and prove they have access to that email account. [1] | If the user's email account has been compromised (e.g. through a phishing attack or password reuse), an attacker could click the verification link and impersonate the user. [1] |
| SMS one-time passcode | A temporary numeric code is sent via SMS to the user's registered mobile phone number. The code must be entered into the website within a short time limit (typically 2-5 minutes) to confirm identity. [1] | The code could be intercepted through SIM swapping (where an attacker convinces the phone provider to transfer the number to a new SIM) or if the phone is stolen. [1] |
(b) Why combining methods is more secure [2]
Using a combination ensures that even if one method is compromised (e.g. a hacker knows the answer to a security question), they still need to bypass additional methods to gain access. [1]
Different methods verify identity using different channels (knowledge, email, phone), reducing the chance that a single attack vector (e.g. phishing) can defeat all of them simultaneously. [1]
