What do Viruses, Trojans, and Other Malware Actually Do to the system?

Question

I don't know I am getting this kind of add at my bottom of the desktop.
I am unable open the add panel or what is that. I remove that from my Task bar.
please help me It seem I have got malware in my computer.

Answer 1

Viruses, Trojans, etc. are collectively known as Malware.

Viruses: The term comes from the biological term, virus. Like virii in real life, a computer virus infects an organism and then spreads by replicating itself.
Trojans: The term is again borrowed from the concept of the "Trojan Horse" from Greek Mythology. A Trojan is a computer application which looks completely harmless on the outside. It is only after you install it that you realize what it actually is, but the damage is done by then.

The amount and extent of damage caused by any malware depends greatly on its purpose. Some malware were written only for fun and may display a limerick on your screen, but nothing more. Others may harvest your data and send it out so that it can be sold to the highest bidder. Some malware exist only to break into some other program in your system and then download its payload which is what actually performs the malicious activities.

Some malware will do absolutely nothing to your system. Stuxnet is a famous example of this. It was written to target only a certain computer and would remain dormant on all others.

Yes, you can always remove a malware from your computer manually. You only need to replicate the exact steps that the anti-malware applications perform. It's possible, I've done it, but it's not easy. And more often than not you'll leave something behind. You should use the specialized software available instead.

The easiest way to prevent malware from infecting your system is to use Linux. As explained by Miami Tom Windows has an inherently broken security mechanism. Linux on the other hand is very strong. If you must stay on Windows, use a good anti-malware tools with a firewall.

Answer 2

I believe we can write an essay on this subject, but the short answer is much more popular. Most explanation below comes from ZDnet.

A computer virus is a form of software or code that is able to copy itself onto computers. The name has become associated with additionally performing malicious tasks, such as corrupting or destroying data.
The Trojan horse is a form of malicious software that often disguises itself as a legitimate tool that tricks the user into installing it so it can carry out its malicious goals.

Other common malware

Spyware is software that monitors the actions carried out on a PC and other devices. That might include web browsing history, apps used, or messages sent. Spyware might arrive as a trojan malware or may be downloaded onto devices in other ways.

Ransomware encrypts the infected system, locking the user out until they pay a ransom -- delivered in bitcoin or other cryptocurrency, in order to get their data back. Like ransomware, Wiper malware has a similar goal: to completely destroy or erase all data from the targeted computer or network. One of the most high profile wipers of recent times was Petya ransomware.

Computer Worm often exploit vulnerabilities in operating systems or software, but are also capable of distributing themselves via email attachments in cases where the worm can gain access to the contact book on an infected machine.

Different types of malware have different targets and methods to achieve their goals. However, they all lead to the same results - impairing users’ benefits.