Computer ScienceCBSE Class 11 · Societal Impact

Cyber Crime, Malware and Cyber Safety Class 11: Phishing, Ransomware, Trojan and Safe Browsing

Updated 17 October 2026 · Fact-checked

Cyber crime is a criminal act in which a computer or network is the target or the tool. Main types are hacking (unauthorised access), eavesdropping (secret interception), phishing (fake messages that steal passwords or OTPs) and ransomware (locks data for payment). Malware such as a virus, trojan horse or adware damages systems; cyber safety means safe browsing, strong passwords and protecting identity and confidential data.

Match each threat to its defence: strong passwords, avoiding public Wi-Fi, never sharing OTPs, and keeping backups.

Illustration drawn for QuestionBuddy.

Understand Cyber Crime, Malware and Cyber Safety: Phishing, Ransomware, Trolls and Safe Browsing (CBSE 11)

Cyber crime is a criminal act where a computer or network is the target or the tool, aimed at a person, group, organisation or country to cause loss, harm or harassment.

Types.

Hacking: gaining unauthorised access to a computer or network. An ethical (white hat) hacker looks for weaknesses with the owner's permission so that they can be fixed; a black hat hacker (cracker) breaks in to steal, damage or make money.
Eavesdropping: secretly intercepting private communication while it is sent, for example on an unsecured public network.
Phishing and fraud: fake emails, messages, calls or websites that look genuine to trick people into giving passwords, card details or OTPs. Identity theft uses stolen personal data to commit fraud in the victim's name.
Ransomware: malware that locks or encrypts a victim's data and demands payment to restore it.
Cyber trolls: post provocative or insulting messages to start quarrels; the advice is not to feed them with replies, and to report and block them.
Cyber bullying: repeated harassment, threats or humiliation of a person through digital media. A victim should not reply, should keep screenshots, block the bully, tell a trusted adult and report to the platform or the cyber cell.

Malware is malicious software.

Virus: attaches itself to a file or program and copies itself when that program runs.
Trojan horse: disguised as useful software; once installed it lets attackers in or steals data; it does not copy itself like a virus.
Adware: floods the user with unwanted advertisements and may track browsing; often bundled with free software.
Defences: updated antivirus, regular backups, system updates, avoiding pirated software and unknown attachments.

Cyber safety.

Safe browsing: known sites with HTTPS, heed browser warnings, avoid unknown links and pop-ups, download from trusted sources, keep the browser updated.
Identity protection: never share passwords or OTPs; use strong, different passwords (letters, digits and symbols, no common words); use two-step verification.
Confidentiality: lock devices, secure Wi-Fi, log out of shared computers, encrypt sensitive files.

Law. India's Information Technology Act, 2000 (amended in 2008) recognises electronic records and digital signatures and lists cyber crimes and penalties, such as hacking and using another person's password. Cyber crime can be reported at a police cyber cell.

Cyber Crime, Malware and Cyber Safety: Phishing, Ransomware, Trolls and Safe Browsing (CBSE 11): key facts

Cyber crimes: hacking is unauthorised access
eavesdropping is secret interception
phishing steals details with fake messages
ransomware locks data for money; Computer is the target or the tool.
Hackers: white hat hacker has permission | black hat hacker (cracker) breaks in to harm or steal; Hacking alone is not always illegal.
Malware: virus attaches and copies itself
trojan is disguised as useful software
adware floods advertisements; A trojan does not self-copy.
Safety steps: HTTPS and trusted sites
strong different passwords
two-step verification
updated antivirus and backups; Never share OTPs.

How to answer Cyber Crime, Malware and Cyber Safety: Phishing, Ransomware, Trolls and Safe Browsing (CBSE 11) questions

To name an attack or malware, look for the key behaviour in the scenario.

1Underline the action: breaking in, listening in, tricking, locking data, annoying posts or adverts.
2Match it to the definition: unauthorised access is hacking, secret listening is eavesdropping, fake genuine-looking message is phishing, payment demanded for data is ransomware.
3For malware ask whether it copies itself (virus), pretends to be useful (trojan) or shows adverts (adware).
4State the safe action: do not click or reply, keep evidence, block, tell an adult, report.
5Quote the IT Act, 2000 only when the question asks about law.

Cyber Crime, Malware and Cyber Safety: Phishing, Ransomware, Trolls and Safe Browsing (CBSE 11) in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

A fake delivery message

Suppose Meera gets an SMS saying "Your parcel is held, pay a small fee at this link and enter your OTP". She has not ordered anything.

Which cyber crime is this and what should she do?

Try it first, then show the solutionSolution

A message made to look genuine, asking for an OTP and money, is phishing.
She should not click or share the OTP, should delete the message, and report it to the bank or the cyber cell if money is at risk.

Answer: Phishing; do not click or share the OTP, and report it.

Memory hook: Genuine look plus urgent request for secrets means phishing.

Tricks to remember Cyber Crime, Malware and Cyber Safety: Phishing, Ransomware, Trolls and Safe Browsing (CBSE 11)

Short memory aids. Say each one aloud once, then use it on a question the same day.

White hat has permission
White hat = permission = ethical; black hat = crack = crime.
Use it when: Hacker types.
Virus copies, trojan tricks, adware annoys
Three words, three behaviours.
Use it when: Malware questions.
Do not feed, do not reply
Trolls and bullies want a reaction: keep evidence, block, report.
Use it when: Cyber bullying answers.

Cyber Crime, Malware and Cyber Safety: Phishing, Ransomware, Trolls and Safe Browsing (CBSE 11): solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Disguised malware · 1 mark · MCQBoard level

Which malware is disguised as useful software?
(a) Virus
(b) Adware
(c) Trojan horse
(d) Ransomware

Try it first, then show the solutionSolution

A trojan horse pretends to be a useful program such as a free game or cleaner.
A virus attaches to files and copies itself instead.

Answer: (c) Trojan horse

Example 2: Virus and trojan · 2 marks · Short answerBoard level

Differentiate between a virus and a trojan horse. (2 marks)

Try it first, then show the solutionSolution

A virus attaches itself to a file or program and copies itself when the program runs, damaging data.
A trojan horse is disguised as useful software and works only after the user installs it; it does not copy itself.

Answer: A virus copies itself and spreads by attaching to files; a trojan pretends to be useful software and does not self-copy.

Example 3: Name the threat · 4 marks · Short answerHarder board level

Name the cyber crime or person in each situation. (4 marks)
(a) An email imitating a bank asks for a password and OTP.
(b) All office files are locked and a payment is demanded.
(c) A person secretly reads messages sent over an open public Wi-Fi.
(d) A security expert tests a company network with its written permission.
(e) Repeated mocking posts target one classmate.
(f) A user posts provocative messages in a forum to start quarrels.

Try it first, then show the solutionSolution

(a) Genuine-looking message that steals secrets: phishing.
(b) Data locked for payment: ransomware.
(c) Secret interception of communication: eavesdropping.
(d) Permission given: ethical (white hat) hacking.
(e) Repeated harassment of a person: cyber bullying.
(f) Provocative posts to start quarrels: cyber trolling.

Answer: (a) Phishing (b) Ransomware (c) Eavesdropping (d) Ethical hacking (e) Cyber bullying (f) Trolling

Example 4: Suspicious SMS case · 5 marks · Case-basedHOTS / competency

Case: Arjun receives an SMS: "Your bank account will be blocked today. Click this link and enter your card number and OTP." The link name looks like his bank's name with extra letters. (5 marks)
(i) Name the crime. (1)
(ii) Give two clues that it is not genuine. (2)
(iii) State two actions he should take. (2)

Try it first, then show the solutionSolution

(i) A message made to look genuine to obtain card and OTP details is phishing.
(ii) Clues: it creates urgency (blocked today); the link is a look-alike address with extra letters; it asks for the OTP and card number, which a real bank does not.
(iii) Actions: do not click the link or share the OTP; report the message to the bank and to the cyber cell, and block the sender.

Answer: (i) Phishing. (ii) Urgent threat; look-alike web address; asks for OTP. (iii) Do not click or share the OTP; report to the bank and cyber cell.

Example 5: Choosing a password · 4 marks · Short answerHarder board level

Riya uses the password riya2010 (her name and birth year) for every site. Explain why this is unsafe and compare it with R!y4#Tz9q2. List two more steps to protect her identity. (4 marks)

Try it first, then show the solutionSolution

riya2010 uses personal details that can be guessed, and using it on every site means one leak exposes all her accounts.
R!y4#Tz9q2 mixes upper and lower case, digits and symbols and has no dictionary word or personal detail, so it is strong.
Use a different strong password for each site.
Turn on two-step verification and never share passwords or OTPs.

Answer: riya2010 is guessable and reused; the second is strong. Use different passwords and two-step verification.

Where students lose marks in Cyber Crime, Malware and Cyber Safety: Phishing, Ransomware, Trolls and Safe Browsing (CBSE 11)

The slips examiners see most often, and what to write instead.

Mistake: Calling every hacker a criminal
Ignoring the white hat category.
Wrong working
Hacking is always illegal
Right working
Ethical (white hat) hacking is done with the owner's permission to fix weaknesses
Do this: Mention permission.
Usually costs: 1 mark
Mistake: Saying a trojan copies itself
Mixing up virus and trojan.
Wrong working
A trojan spreads by copying itself
Right working
A virus copies itself; a trojan is disguised software that does not self-copy
Do this: Use the behaviour words.
Usually costs: 1 mark
Mistake: Advising the victim to reply to a bully
Treating it like an argument.
Wrong working
Reply and warn the bully
Right working
Do not reply; keep screenshots, block, tell an adult and report
Do this: Do not feed.
Usually costs: 1 to 2 marks

Exam tips

Give a one-line definition and one example for each type of cyber crime.
Include the word unauthorised in the hacking definition.
Name both the crime and the safe action in case-based answers.
Mention the IT Act, 2000 (amended 2008) when law is asked.

Practice questions on Cyber Crime, Malware and Cyber Safety: Phishing, Ransomware, Trolls and Safe Browsing (CBSE 11)

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
Which of these is NOT a recommended step for a victim of cyber bullying?
(a) Keep screenshots as evidence
(b) Reply angrily to the bully
(c) Block the bully
(d) Report to the platform
Hint
Do not feed.
Answer
(b) Reply angrily to the bully
Q2 · 1 mark · Assertion-reasonHarder board level
Assertion (A): All hacking is illegal.
Reason (R): Ethical hackers test the security of a system with the permission of its owner.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Hint
White hat.
Answer
(d) A is false, but R is true.
Q3 · 4 marks · Short answerHarder board level
Differentiate between (a) hacking and eavesdropping, and (b) adware and ransomware. (4 marks)
Hint
Use the key behaviour.
Answer
(a) Hacking is unauthorised access to a computer or network; eavesdropping is secretly intercepting communication while it is being sent. (b) Adware shows unwanted advertisements and may track browsing; ransomware locks or encrypts data and demands payment to restore it.
Q4 · 4 marks · Short answerHarder board level
List four safe-browsing practices and four ways to protect identity online. (4 marks)
Hint
Use the cyber safety lists.
Answer
Safe browsing: use known sites with HTTPS; heed browser warnings; avoid unknown links and pop-ups; download only from trusted sources; keep the browser updated. Identity: never share passwords or OTPs; strong different passwords; two-step verification; share few personal details; do not post Aadhaar or bank data.
Q5 · 5 marks · Case-basedHOTS / competency
Case: In a school lab, pop-up advertisements appear on every computer after a teacher installed a free game from an unknown website. A week later a file on the shared drive will not open and a note asks for money to unlock it. (5 marks)
(i) Name the two kinds of malware or attack seen. (2)
(ii) How did they probably enter? (1)
(iii) Give two preventive measures. (2)
Hint
One shows ads; the other locks data.
Answer
(i) Adware (unwanted pop-ups) and ransomware (locked file with a payment demand). (ii) Through the free software from an unknown site, which may have carried the adware and the ransomware. (iii) Keep antivirus updated, take regular backups, avoid pirated or unknown software and unknown attachments, and report to the cyber cell.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.What is phishing?Show answer
Fake messages or sites that look genuine to steal passwords, card details or OTPs.
2.What does ransomware do?Show answer
Locks or encrypts data and demands payment.
3.Who is a white hat hacker?Show answer
An ethical hacker who tests a system with the owner's permission.
4.Which Indian law covers cyber crime?Show answer
The Information Technology Act, 2000, amended in 2008.
5.What should a trolling victim do?Show answer
Not reply; report and block.

Cyber Crime, Malware and Cyber Safety: Phishing, Ransomware, Trolls and Safe Browsing (CBSE 11): frequently asked questions

Is a virus the same as malware?

No; virus is one kind of malware. Trojans and adware are other kinds.

Is HTTPS enough to prove a site is safe?

No; it shows that the connection is secured, but you should still check the site name and avoid unknown links.

Where is cyber crime reported?

At a police cyber cell, and to the platform or bank concerned.