Study Material and Notes of Chapter 6 Security Threats and Safety Measures Computer Class 9th


• With the increasing use of the internet, there is also increase in threats to the computers.

• The main objectives of these threats is to destroy the data and to steal the vital information stored
in computers.


• A computer virus is a program usually hidden within another simple program.

• These programs destroy data and perform other malicious actions by producing copies of itself and inserting them into other programs or files.

• These are created with a specific target in mind such as data theft or destruction of software.

• Viruses are of different types but a common virus is macro virus.

• Macro Virus: It is series of programming steps that are stored in a single location.

→ These can be embedded in the program files.

→ These viruses created with the intention of fooling the user can deceive them in sharing confidential information.

→ The virus using macro files are most popular as they are:
♠ Easy to write.
♠ Can infect more people faster as they exchange documents and data frequently
♠ Can easily infect any computer capable of running Office and Internet.

→ Macro viruses can corrupt data, create new files, move text, flash colors, insert pictures, send files across the Internet, and format hard drives.

→ Macro viruses modify registries, forward copies of it through emails, look for passwords, copy documents, and infect other programs.

→ Examples of Macro Viruses: Wazzo, W97M etc.


• Worms are computer programs that replicate copies of themselves.

• They are very similar to viruses however many difference are present between them.

• Difference between Worms and Viruses
→ Viruses often, but not always, contain some functionality that will interfere with the normal
use of a computer or a program however, worms exist as separate entities; they do not attach themselves to other files or programs.

• Some examples of the worst Worms that impacted we are:

→ Jerusalem is one of the earliest worms that spread in 1987. It used to delete files that were executed on each Friday the 13th.

→ In 1991, thousands of machines running MS-DOS were hit by a new worm, Michelangelo. The virus would overwrite the hard disk or change the master boot record of infected hosts.

→ In 2007 Storm Worm hit the computers.The worm gather data on the host machine, to sending infected emails to others.

• Worm mainly spreas through email attachments.

Trojan Horses

• A Trojan horse is a program that claims to rid your computer of viruses but instead introduces viruses into the system.

• The Trojan program does not attach itself to the files like a virus nor replicate itself like a worm but it does provide unauthorized access to user’s computer.

• These mostly spread through internet downloads and online gaming programs.

• The software makes infected computer slow and will exhibit pop-ups from time to time. Eventually, the computer will cease to operate, or crash.

• The best way to avoid the Trojans is to adopt safe download practices. Always download any program from trusted source.

• Examples: I love you


• A Spyware is a program used to spy on the computer system. This program will try to get all the confidential and sensitive information such as your bank account numbers, passwords etc.

• Spyware can also change the configuration of your computer, generally without obtaining your consent first.

• SpyWare software covertly install the software during the installation of other software that is being downloaded such as music or video or a file-sharing program.

• After installation, the Spyware monitors user activity on the Internet and transmits that information in the background to someone else.

• SpyWare have the ability to monitor keystrokes, scan files on the hard drive, snoop other applications, such as chat programs or word processors.

• Examples are CoolWebSearch, Internet optimizer and Zango.


• Malware is short for “malicious software.” 

• Malware is any kind of unwanted software that is installed without your adequate consent.

• Malware damage the data or functionality of the computer or network.

• Virus, Trojans etc are examples of Malware.


• The term “spam” refers to unsolicited commercial email (UCE) or unsolicited bulk email (UBE). 

• Spam simply means irrelevant or inappropriate messages sent on the Internet to a large number of recipients.

• Unsolicited email mostly contains advertisements for services or products.

• Most common spam includes:
→ Phishing scams, a very popular and dangerous form of email fraud
→ Foreign bank scams or advance fee fraud schemes
→ Other “Get Rich Quick” or “Make Money Fast” (MMF) schemes
→ Quack health products and remedies.

• Spam email clogs your email accounts and uses unnecessary server space.

• It is never possible to completely stop the Spam email because Internet is a public platform. However precaution can be taken while looking at an unknown email addresses.

Hackers and Crackers

• Hackers and crackers are the software programmers who use dubious ways to get control over your computer and systems.

• Their main objective is to gain control over a computer so that they can get the sensitive confidential information.

• They use information against you by stealing money, personal data, pictures, bank details and government military information, so on and so forth.

• Hackers were the gifted programmers who gain access to the systems or network to show case the security loopholes to the administrators.

• Crackers have an end goal of destroying data and network for personal monetary gains.

AntiVirus Tools

• Anti Virus tools are the software programs that help us detect the virus in emails or files and hence protect our computers.

• These tools can detect virus, worms, Trojans as well as spyware and adware.

• They block us from visiting unsafe websites, and also downloading unsafe programs from such websites.

• They protect us from identity thefts and threats from phishing websites.

• Examples are Norton, Mcafee, K7, Quickheal etc.

Data Backup and Security

• The basic principal on data back up is very simple, just make another copy of the data and keep it elsewhere than on the same computer.

• This guarantees that once the data on your computer gets corrupted due to a threat, you can reload the data again on your computer once it has been rectified.

• We can use external hard drives and smart devices are to back up the data.

• Some guideing principles to use the computers securely:

→ Using Security software such as Norton antivirus, Symantec etc.
→ Never share passwords
→ Beware of email attachments form unknown sources
→ Do not randomly download material from websites which has not been checked for security
→ Never propagate hoax or chain emails
→ Always logout your laptop or computer
→ Restrict remote access
→ Frequently back up important data and files
→ Use encryption or sites that use encrypted data

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