Types of Computer Virus

Back to: COMPUTER SCIENCE SS1

 

Welcome to class!

In today’s class, we will be talking about types of computer virus. Enjoy the class!

 Types of Computer Virus

1. Memory Resident Viruses – They usually fix themselves inside the computer memory. They get activated every time the OS runs and end up infecting other opened files. They hide in RAM. This type of virus is permanent which dwells in the RAM memory. From there it can overcome and interrupt all of the operations executed by the system: corrupting files and programs that are opened, closed, copied, renamed etc. Memory Resident Viruses Include:
   • CMJ
   • meve
   • randex
   • mrklunky
2. Worm: This program is very similar to a virus and has the ability to self-replicate leading to negative effects on your computer. Worm Viruses Include:
   • lovgate.F
   • sobig.D
   • trile. C
   • PSWBugbear.B
   • Mapson
3. Trojans or Trojan Horses: Another unsavoury breed of malicious code (not a virus as well) are Trojans or Trojan horses, which unlike viruses do not reproduce by infecting other files, nor do they self-replicate like worms. Trojans can illegally trace important login details of users online. For example, E-Banking is very common among users, therefore, the vulnerability of tracing your login details whenever your PC is working without any strong powerful antivirus installed.
4. Browser Hijacker: This virus can spread in many different ways including a voluntary download. If infects certain browser functions especially in the form of re-directing the user automatically to certain sites. A good example is a cool web search. This type of virus, which can spread itself in numerous ways including voluntary download, effectively hijacks certain browser functions, usually in the form of re-directing the user automatically to particular sites
5. Polymorphic Virus: They encode or encrypt themselves in a different way every time they infect your computer. They use different encryption and algorithms. This makes it difficult for the antivirus software to locate them using signature or string searches (since they are very different in each encryption). Polymorphic Viruses Include:
   • Marburg
   • tuareg
   • Satan bug
   • elkern
6. FAT Virus: The file allocation table or FAT is the part of a disk used to connect information and is a vital part of the normal functioning of the computer. This type of virus attack can be especially dangerous, by preventing access to certain sections of the disk where important files are stored. Damage caused can result in information losses from individual files or even entire directories.
7. Overwrite Viruses: These types of viruses delete any information in a file they infect, leaving them partially or completely useless once they are infected. Once in the computer, they replace all the file content but the file size doesn’t change. Overwrite Viruses Include:
   • Trj.Reboot
   • way
   • trivial.88.D
8. Companion Viruses: Companion viruses can be considered file infector viruses like a resident or direct action types. They are known as companion viruses because once they get into the system they “accompany” the other files that already exist. In other words, in order to carry out their infection routines, companion viruses can wait in memory until a program is run (resident viruses) or act immediately by making copies of themselves (direct action viruses). Some examples include: Stator, Asimov.1539, and Terrax.1069

Evaluation

1. What are computer viruses?
2. List and explain the various types of computer viruses.

 

In our next class, we will be talking about Application Software. We hope you enjoyed the class.

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