The free game that was not free
Sam downloads a free game from a strange website. It works. But a week later her phone is slow and the battery is empty by lunch.
Then a message appears: "Your photos are locked. Pay 200 pounds to get them back."
What happened? Sam installed software that was built to cause harm.
Key words
| Word | What it means | Example |
|---|---|---|
| Malware | Software made to cause harm. The word is short for "malicious software". | a virus |
| Virus | Malware that hides inside a file and spreads when you open it. | a bad attachment |
| Worm | Malware that spreads by itself across a network (linked computers). | a copy that jumps from PC to PC |
| Trojan | Malware that pretends to be a useful program. | a fake free game |
| Keylogger | Malware that records every key you press. | it steals a typed password |
| Spyware | Malware that secretly watches what you do. | it sees the sites you visit |
| Ransomware | Malware that locks your files until you pay. | a locked photo folder |
| Botnet | A group of infected devices that one attacker controls. | 10,000 hacked cameras |
| DoS | Denial of service. Too many requests make a website stop working for real users. | a shop site that will not load |
| DDoS | Distributed DoS. The requests come from many devices at once. | a botnet attack |
The cells students fill in are left blank in this preview.
Quick check: which is which?
Have a go
Quick check: which is which?
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Six kinds of malware
| Type | What it does | Harm to a person | Harm to a company |
|---|---|---|---|
| Virus | Hides in a file and spreads when it is opened | Damaged files | Damaged files and lost work |
| Worm | Spreads alone across a network | A slow device | A whole network slows down |
| Keylogger | Records key presses | Stolen passwords | Stolen passwords and secrets |
| Ransomware | Locks files until you pay | Lost photos | Work stops. Money is demanded |
| Spyware | Secretly watches you | Loss of privacy | Loss of secrets |
| Remote access trojan | Lets the attacker control the device from another place | Camera and files seen | Attacker can move to other devices in the network |
The cells students fill in are left blank in this preview.
Too many visitors: DoS
A shop has one checkout. It serves one customer a minute. What if 600 fake customers stand in the queue?
Real customers wait a very long time. Then they leave.
A website is like that checkout. A DoS attack sends too many requests. The site is too busy for real users.
Try it: when is a server overloaded?
# A server can answer 100 requests each second.
capacity = 100
real_users = 40
attack = 0
total = real_users + attack
print("Requests this second:", total)
print("Overloaded?", total > capacity)
# Change attack to 500 and run it again.
DoS or DDoS?
data-callouts.important.label
DoS: the requests come from one place. You can block that one address.
DDoS: the requests come from thousands of places. It is much harder to block.