Data security: availability

Name:

Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

1. Which statement best describes availability in data security?

A Authorised users can reach data and systems when they need them

B Only one person is ever allowed to see the data

2. A school server's hard drive fails during exams and students cannot open their files. Which part of security is affected?

A Confidentiality

B Availability

3. Which action helps protect availability if a hardware failure happens?

A Keeping regular backups and a spare system

B Using a longer username

4. A DoS attack floods a website with so many requests that real users cannot log in. What does it threaten?

A Availability

B Data entry validation

5. True or false: A system that is switched off by a power failure has lost availability.

A False

B True

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1Availability		AAn attack that floods a server with traffic so real users cannot reach it
2DDoS attack		BA single point of failure threatens availability. One failed server stops all users, and with no backup the data may be lost.
3A hardware failure such as a dead disk can make data unavailable, so a copy is kept on a second drive		CAuthorised users can reach data and systems when they need them
4A backup stored off-site lets a school restore data after a failure or an attack and get users working again		DTurning off the firewall leaves the system open to attacks such as DDoS, which can knock the website offline for authorised users.
5Only one server, no backup. If it fails, the school can just wait.		ERAID 1 mirror: disk A and disk B hold the same data
6Firewall switched off to make the website faster.		Frestore(backup_2026_03_01)

Definitions

Availability

Fill in the Blanks

Complete each line of code by filling in the missing parts.

if serverStatus = "down" ____ print("Switch to backup server") end if

if requestsPerMin _ limit then block(ipAddress) end if

if diskFailed = true then _______(backup) end if

_____ serverUp = false do reconnect(server) end while

hoursUp <- 98 totalHours <- 100 uptime <- hoursUp _ totalHours * 100

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A if disk <- "failed" then

B server <- "backup"

C else

D server <- "main"

E end if

Question 2

A attempts <- 0

B while attempts > 5

C input password

D attempts <- attempts + 1

E print "Account locked"

Question 3

A files <- 120

B backedUp <- 0

C for i from 0 to files

D backedUp <- backedUp + 1

E print backedUp

Question 4

A serverUp <- false

B if serverUp = true then

C print "Use backup server"

D end if

Question 5

A lastBackup <- 9

B limit <- 7

C if lastBackup > limit then

D print Backup is overdue

E end if

Answer Key

Data security: availability

Section A: Quick Questions

A — Authorised users can reach data and systems when they need them

B — Availability

A — Keeping regular backups and a spare system

A — Availability

B — True

Section B: Match the Pairs

Availability → Authorised users can reach data and systems when they need them

DDoS attack → An attack that floods a server with traffic so real users cannot reach it

A hardware failure such as a dead disk can make data unavailable, so a copy is kept on a second drive → RAID 1 mirror: disk A and disk B hold the same data

A backup stored off-site lets a school restore data after a failure or an attack and get users working again → restore(backup_2026_03_01)

Only one server, no backup. If it fails, the school can just wait. → A single point of failure threatens availability. One failed server stops all users, and with no backup the data may be lost.

Firewall switched off to make the website faster. → Turning off the firewall leaves the system open to attacks such as DDoS, which can knock the website offline for authorised users.

Section C: Definitions

Availability — Authorised users can reach data and systems when they need them. Hardware failure and attacks can threaten it, so backups and protection keep a system running.

Section D: Fill in the Blanks

if serverStatus = "down" then
    print("Switch to backup server")
end if

if requestsPerMin > limit then
    block(ipAddress)
end if

if diskFailed = true then
    restore(backup)
end if

while serverUp = false do
    reconnect(server)
end while

hoursUp <- 98
totalHours <- 100
uptime <- hoursUp / totalHours * 100

Section E: Spot the Error

A — The condition needs the comparison operator = to check whether the disk has failed. <- assigns a value and does not compare. It should be: if disk = "failed" then.

B — attempts starts at 0, so attempts > 5 is false straight away and the lockout loop never runs. An attack could keep guessing passwords. It should be: while attempts < 5.

C — Starting at 0 makes the loop run 121 times, so it counts one more backup than there are files. The backup count would be wrong. It should be: for i from 1 to files.

B — The backup server should be used when the main server is down, so the test must be serverUp = false. As written, it switches to the backup while the main server is working.

D — The text to display must be in quotation marks. Without them, Backup is overdue is treated as code and not as a string. It should be: print "Backup is overdue".