Most Common Types of Viruses and Other Malicious Programs

1. File Infectors

This kind of virus infects programs or executable files (files by having an .EXE or .COM extension). When one of these simple programs operates, directly or not directly, herpes is activated, producing the harmful effects it’s programmed to handle. Nearly all existing infections is associated with this category, and could be classified with respect to the actions they execute.

2. Multipartite Viruses

Multipartite infections are distributed through infected media in most cases hide within the memory. Progressively, herpes moves towards the boot sector from the hard disk and infects executable files around the hard disk and then over the computer.

3. Direct Action Viruses

The primary reason for herpes would be to replicate and do something when it’s performed. Whenever a specific condition is met, herpes goes into action and infect files within the directory or folder that it’s in as well as in directories which are specified by the AUTOEXEC.BAT file PATH. This batch file is definitely found in the root list of hard disk and performs certain operations once the computer is booted.

4. Overwrite Viruses

Virus of the kind is characterised because it deletes the data within the files it infects, rendering them partly or totally useless once they’ve been infected.

The only method to clean personal files infected by an overwrite virus would be to delete the file completely, thus losing the initial content.

Examples of this virus include: Way, Trj.Reboot, Trivial.88.D.

5. Boot Virus

This kind of virus affects the boot sector of the floppy or hard disk drive. This can be a crucial a part of a disk, by which info on the disk is stored plus a program which makes it possible as well (start) the pc in the disk.

The easiest way of staying away from boot infections is to make sure that diskettes are write-protected rather than start your pc by having an unknown floppy disk within the disk drive.

Examples of boot viruses include: Polyboot.B, AntiEXE.

6. Macro Virus

Macro infections infect files which are produced using certain applications or programs which contain macros. These small-programs have the ability to automate number of operations so they are carried out like a single action, therefore saving the consumer from getting to hold them out one at a time.

Examples of macro viruses: Relax, Melissa.A, Bablas, O97M/Y2K.

7. Directory Virus

Directory viruses change the paths that indicate the location of a file. By executing a program (file with the extension .EXE or .COM) which has been infected by a virus, you are unknowingly running the virus program, while the original file and program have been previously moved by the virus.

Once infected it becomes impossible to locate the original files.

8. Polymorphic Virus

Polymorphic infections secure or encode themselves in different ways (using different algorithms and file encryption keys) when they infect a method.

This will make it impossible for anti-infections to locate them using string or signature searches (since they’re different in every file encryption) as well as permits them to create a lot of copies of themselves.

Examples include: Elkern, Marburg, Satan Bug, and Tuareg.

9. Resident Viruses

This type of virus is a 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.

Examples include: Randex, CMJ, Meve, and MrKlunky.

10. Encrypted Viruses

This kind of infections includes encrypted malicious code, decrypted module. The infections use encrypted code technique which will make anti-virus software hardly to identify them. The anti-virus program normally can identify this kind of infections once they try spread by decrypted themselves.

11. Companion Viruses

Companion infections can be viewed as file infector infections like resident or direct action types. They are classified as companion infections because after they enter into the machine they “accompany” another files that already exist. Quite simply, to be able to execute their infection routines, companion infections can stand in memory until a course operates (resident infections) or act immediately by looking into making copies of themselves (direct action infections).

Some examples include: Stator, Asimov.1539, and Terrax.1069

12. Network Virus

Network infections quickly spread via a Local Network Area (LAN), and often through the internet. Generally, network infections multiply through shared sources, i.e., shared drives and folders. Once the virus infects a pc, it searches with the network to fight its new potential prey. Once the virus finishes infecting that computer, it moves to the next and also the cycle repeats itself.

The most dangerous network viruses are Nimda and SQLSlammer.

13. Nonresident Viruses

This kind of infections is comparable to Resident Infections by utilizing replication of module. On top of that, Nonresident Infections role as finder module which could infect to files if this found one (it’ll select a number of files to contaminate every time the module is performed).

14. Stealth Viruses

Stealth Infections is some kind of infections which attempt to trick anti-virus software by intercepting its demands towards the operating-system. It’s capability to hide itself from some anti-virus software packages. Therefore, some anti-virus program cannot identify them.

15. Sparse Infectors

To be able to spread broadly, the herpes virus must make an effort to avoid recognition. To reduce the prospect of its being discovered the herpes virus can use a variety of different techniques. It could, for instance, only infect every 20th time personal files is performed it could only infect files whose lengths are within narrowly defined ranges or whose names start with letters inside a certain selection of the alphabet. There are lots of other options.

16. Spacefiller (Cavity) Viruses

Many infections take the easiest way out when infecting files they just attach themselves towards the finish from the file after which change the beginning of this program in order that it first suggests herpes after which towards the actual rule. Many infections which do this implement some stealth techniques which means you aren’t seeing the rise in file length once the virus is active in memory.

A spacefiller (cavity) virus, however, tries to be clever. Some program files, for various reasons, have empty space within them. This empty space may be used to house virus code. A spacefiller virus tries to install itself within this empty space whilst not damaging the particular program itself. The advantage of this would be that the virus then doesn’t increase the size of this program and may avoid the requirement for some stealth techniques. The Lehigh virus was an earlier illustration of a spacefiller virus.

17. FAT Virus

The file allocation table or FAT is negligence a disk accustomed to connect information and is a crucial area of the normal functioning from the computer.

This kind of virus attack could be especially harmful, by stopping use of certain parts of the disk where important files are stored. Damage caused can lead to information losses from individual files or perhaps entire directories.

18. Worms

A earthworm is technically not really a virus, however a program much like the herpes virus it is able to self-replicate, and can result in unwanted effects in your system and more importantly they’re detected and eliminated by antiviruses.

Examples of worms include: PSWBugbear.B, Lovgate.F, Trile.C, Sobig.D, Mapson.

19. Trojans or Trojan Horses

Another unsavory variety of malicious code (not really a virus too) are Trojans or Trojan viruses horses, which unlike infections don’t reproduce by infecting other files, nor will they self-replicate like worms.

20. Logic Bombs

They aren’t considered infections as they do not replicate. They aren’t even programs themselves but instead camouflaged segments of other individuals.

Their objective would be to destroy data on the pc once certain conditions happen to be met. Logic bombs go undetected until launched, and also the results could be destructive.

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