How does Viruses (Malware, Trojans, Spywares) work?

A virus operates by inserting or attaching itself to a legitimate program or document that supports macros in order to execute its code. In the process, viruses have the potential to cause unexpected or damaging effects, such as harming the system software by corrupting or destroying data.

But, A computer with no link to an external device or computer is free from the viruses threats arising otherwise. However, it is not an ideal solution for a human being or a computer to stay aloof in order to mitigate any viruses threats, as the world at present is on its way to become fully connected.

Malware

Malware is a short term used for malicious software. It is any software developed with an intention to damage hardware devices, steal data, or cause any other trouble to the user.

Various types of malware have been created from time-to-time, and large-scale damages have been inflicted. Many of these malware programs have been identified and counter measures have been initiated.

Various types of malware are :

Virus
Worms
Ransomware
Adware
Keyloggers
Trojan Horses
Spyware
Phishing

Worms

The Worm is also a malware that incurs unexpected or damaging behavior on an infected computer system. Worms are standalone programs that are capable of working on its own. A worm replicates on its own and can spread to other computers through the network. Some prominent examples of worms include Storm Worm, Sobig, MSBlast, Code Red, Nimda, Morris Worm, etc.

Ransomware

Ransomware is a type of malware that targets user data. It either blocks the user from accessing their own data or threatens to publish the personal data online and demands ransom payment against the same. Some ransomware simply block the access to the data while others encrypt data making it very difficult to access.

Adware

An Adware is a malware that is created to generate revenue for its developer. An adware displays online advertisements using pop-ups, web pages, or installation screens. Once an adware has infected a substantial number of computer systems, it generates revenue either by displaying advertisements or using “pay per click” mechanism to charge its clients against the number of clicks on their displayed ads.

Keyloggers

A keylogger can either be malware or hardware. The main purpose of this malware is to record the keys pressed by a user on the keyboard. A keylogger makes logs of daily keyboard usage and may send it to an
external entity as well.

One strategy to avoid the threat of password leaks by keyloggers is to use a virtual keyboard while signing into your online accounts from an unknown computer.

Spyware

It is a type of malware that spies on a person or an organization by gathering information about them, without the knowledge of the user. It records and sends the collected information to an external entity without
consent or knowledge of the user.

Spyware usually tracks internet usage data and sells them to advertisers. They can also be used to track and capture credit card or bank account information, login and password information or user’s personal identity.

Trojan Horses

A Trojan Horse program has the appearance of having a useful and desired function.
It neither replicates nor copies itself, but causes damage or compromises the security of the computer.
This must be sent by someone or carried by another program and may arrive in the form of a joke program or software of some sort.
These are often used to capture your logins and passwords.

Examples of Trojan Horses :

Remote Access Trojans (RAT)
IRC Trojans
Backdoor Trojans

How Malware Spread ?

Malware is a program that must be triggered or somehow executed before it can infect your computer system and spread to others. Here are some examples on how malware is distributed: