How do viruses, trojans work ?

A Virus is actually a software in itself that resembles a real program. It often attaches itself to a legitimate or normal program and in a sense piggybacks on it. What I mean by that word is whenever the program runs, the virus runs along with it. It can then replicate itself and affect some other program that is linked to the original program. Some types of viruses attack the boot sector of your device. Thus it will execute itself each time you start your system. Other types of viruses reside inside and will need an action on the part of the user to launch it. For instance, a virus embedded within an email message can execute itself only when you open or run the attachment.

Worms are the types of viruses that keep replicating themselves. They go on infecting one application after another until whole of your system collapses.
Trojan Horse is a kind of malware that disguises itself as a legitimate program. These are generally fall into the category of meticulously engineered pieces of software programs. They make you believe that they do something else, but in actuality they are intended at hacking into your system. These are generally developed by hackers. Trojans are not capable of self replicating. That is the major difference between a Trojan and a virus.

Trojan is one of the miscellaneous virus tools which represent a backdoor into your PCs. It is made up of simple coding in a batch file that could involve in any programs. It is easily injectable and also named as system file. There are some of the ways in which it enters into your systems like Email attachments, application .exe files, unauthorized web pages, software downloads and file sharing networks.

Trojan is also named as Trojan horse. It is one type of malware. Normally these malware are handled by hackers and cyber thieves. They used to enter in unauthorized manner into another user's system. Once this malware is injected into another users system, then the hackers can easily monitor the users system. They can easily delete, modify, copy, block and even disrupt the computers performances and networks. This Trojan does not self replicate like other malware or viruses.

Android has Linux based kernel so the security works a lot differently than the desktop operating system. The Android OS has plenty of security layers in order to avoid the virus and Trojans to affect your device. Here are some of the security issues that may arise.

Virus

Virus is a program that is written specifically to exploit security backdoor. So let's say there is root permission exploit that may get exploited. It goes through the system and affects the security loophole. It tries to damage the system from that point forward. Some of the virus replicate themselves and then another virus can spread if the virus manages to connect to the internet. Depending on the infection designed by the Virus - so the files, folders and apps including the base operating system. The virus usually requires a root access to damage the operating system.

Trojan

Trojan horse is a program which on the face of it does not damage the system. However, it acts as a host for the possible security exploit. And the security viruses, malware usually hide inside such program. It activates these security exploits and rest of the damage to the Android device. Often these programs are part of the adult programs, wallpapers program, slideshow and other such programs. And if you install such apps then they may bypass the security and then root can be taken over by the security exploit.

Working of Antivirus in Android

Antivirus apps usually work on the basis of the patterns in security. They find out patterns of trojan and virus. And then they are solving the security issue. The pattern for such security issue is now part of virus definition. These definitions are loaded by the antivirus and they get rid of the security issues as they scan for those patterns. Android antivirus protects the root user privilege by limiting access to certain patterns. And that way the phone is often protected from basic exploits.

Yes, it is definitely true that some Android viruses can root your phone and get installed as a system app which cannot be removed even by factory reset. Here I am explaining the ways viruses and Trojans can harm your system and what are the basic differences between the two.

Virus
A computer virus is a small program which is written to change the way a computer operates, without taking the permission of the user and doing the same even without his knowledge . A virus has to have two criteria:

It must operate by itself placing its own code within the path of execution of a different program. It has to replicate itself.

Trojan horse
Trojan horses are mostly impostors. They are files that appears to be something important, but, actually they are malicious. The major difference between a Trojan horse and true viruses is that, they cannot replicate themselves, as on principle the viruses do. Trojans would essentially contain malicious code, which, when getting triggered, would cause loss, or better called stealing of data. For a Trojan horse to spread, it needs you to invite these programs to your computers. for example, it can be as simple as opening an unknown email attachment.