Pariksha SaathiLesson 10 of 10 · Computer Knowledge
Cyber Security, the IT Act 2000 and Database (DBMS and SQL) Basics
Drafted with AI assistance and fact-checked on 28 October 2026; not yet read line by line by a human editor. Spotted a mistake? Tell us. Editorial standards & corrections
Malware
Malware is any software written to harm a computer or its user. A virus attaches itself to a program or file and spreads when that file is run or shared; Brain, written in Pakistan in 1986, is called the first virus for IBM PCs. A worm is a standalone program that copies itself across networks without any user action; the Morris worm of 1988 was one of the first on the internet. A Trojan horse, named after the wooden horse of Greek legend, looks like useful software but secretly does harm, such as opening a backdoor, and unlike a virus it does not replicate. Ransomware encrypts the victim's files and demands payment for the key, as WannaCry did in 2017. Spyware secretly collects information, a keylogger records keystrokes to steal passwords, adware shows unwanted advertisements, and a botnet is a group of infected computers (zombies) controlled remotely by an attacker.
Attacks
Phishing uses fake emails or websites that imitate a bank or other trusted body to trick people into revealing passwords, card numbers or OTPs; by phone call it is vishing and by SMS smishing. Spoofing is faking an identity, such as a forged email sender, caller ID or IP address. Pharming redirects users from a real website to a fake one, and a denial-of-service (DoS) attack floods a server with requests until it stops working; a DDoS attack does this from many computers, often a botnet. Others are the man-in-the-middle attack (secretly intercepting communication), the brute-force attack (trying every possible password) and social engineering (manipulating people rather than machines).
Defences
A firewall is hardware or software that monitors traffic between a trusted network and the internet and blocks whatever its rules do not allow. Antivirus software detects and removes malware by matching known signatures and watching for suspicious behaviour, so it must be updated regularly. Encryption turns readable plaintext into unreadable ciphertext with a key. Symmetric encryption (such as AES) uses one shared key, while asymmetric or public-key encryption (such as RSA, 1977) uses a public key to encrypt and a private key to decrypt. A digital signature is made with the sender's private key and checked with the sender's public key, proving who sent a message and that it was not altered. Two-factor authentication asks for two different kinds of proof out of three: something you know (password or PIN), something you have (a phone receiving an OTP, or a card) and something you are (fingerprint or face).
The IT Act 2000
The Information Technology Act, 2000, India's main law on cybercrime and electronic commerce, came into force on 17 October 2000. Based on the UNCITRAL Model Law on Electronic Commerce, it gives legal recognition to electronic records and digital signatures, and Certifying Authorities licensed by the Controller of Certifying Authorities issue Digital Signature Certificates. Section 43 provides compensation for damage to computer systems, Section 65 punishes tampering with computer source code and Section 66 covers computer-related offences such as hacking. The 2008 amendment added offences such as identity theft (66C), cheating by personation (66D), violation of privacy (66E) and cyber terrorism (66F, punishable with imprisonment up to life), and gave CERT-In a legal role as the national agency for cyber security incidents. Section 66A, on offensive online messages, was struck down by the Supreme Court in Shreya Singhal v. Union of India in 2015.
Databases and DBMS
A database is an organised collection of related data, and a DBMS (Database Management System) is the software that creates, stores, updates and retrieves it while reducing duplication, keeping data consistent and controlling access; MySQL, Oracle, PostgreSQL and MS Access are examples. In the relational model, proposed by E. F. Codd of IBM in 1970, data is kept in tables called relations. A row is a record or tuple, a column is a field or attribute, the number of columns is the degree and the number of rows is the cardinality.
Keys
A primary key uniquely identifies each record in a table and can be neither empty (NULL) nor repeated, like a roll number. Every field, or set of fields, that could serve as the primary key is a candidate key, and the candidates not chosen are alternate keys. A composite key is made of two or more columns together. A foreign key is a field in one table that refers to the primary key of another table; it links the two tables and keeps their references valid, which is called referential integrity.
SQL in outline
SQL (Structured Query Language) was developed at IBM in the 1970s and became an ANSI standard in 1986. DDL (Data Definition Language) defines structure with CREATE, ALTER, DROP and TRUNCATE. DML (Data Manipulation Language) changes data with INSERT, UPDATE and DELETE, and SELECT queries it, as in SELECT name FROM students WHERE marks > 60. DCL (Data Control Language) gives and takes away rights with GRANT and REVOKE. TCL (Transaction Control Language) manages transactions with COMMIT, ROLLBACK and SAVEPOINT. DROP removes a whole table, TRUNCATE removes all its rows but keeps the structure, and DELETE removes only the rows chosen.
Key facts
- A virus needs a host file and user action to spread; a worm spreads by itself over networks; a Trojan disguises itself as useful software and does not replicate.
- Ransomware encrypts files and demands payment (WannaCry, 2017); spyware secretly gathers data; a keylogger records keystrokes.
- Phishing: fake email or website; vishing: by voice call; smishing: by SMS; spoofing: faking a sender's identity.
- A firewall filters network traffic by rules; antivirus detects malware by signatures and must be kept updated.
- Symmetric encryption uses one key (AES); asymmetric uses a public and a private key (RSA); a digital signature is made with the sender's private key.
- Two-factor authentication combines two of: something you know (PIN), something you have (phone for OTP, card) and something you are (fingerprint).
- IT Act 2000 came into force on 17 October 2000, based on the UNCITRAL Model Law; amended in 2008; Section 66A struck down in the Shreya Singhal case (2015).
- Section 66C identity theft, 66D cheating by personation, 66E violation of privacy, 66F cyber terrorism (up to life imprisonment).
- Primary key: unique and never NULL; foreign key: refers to another table's primary key; candidate keys not chosen become alternate keys.
- SQL groups: DDL (CREATE, ALTER, DROP, TRUNCATE), DML (INSERT, UPDATE, DELETE, SELECT), DCL (GRANT, REVOKE), TCL (COMMIT, ROLLBACK, SAVEPOINT).
Quick revision
Virus (needs a host), worm (spreads itself), Trojan (disguised, does not replicate), ransomware (WannaCry 2017), spyware, keylogger, botnet; phishing, vishing, smishing, spoofing, pharming, DoS/DDoS; firewall, antivirus, encryption (AES symmetric, RSA public-key), digital signature, two-factor authentication; IT Act 2000 in force 17 October 2000, amended 2008, 66A struck down 2015; DBMS, relational model (Codd 1970); primary, candidate, foreign keys; SQL DDL, DML, DCL, TCL.