Computer Virus:
Computer viruses are small software programs that are designed to spread from one computer to another and to interfere with computer operation.
Computer viruses are often spread by attachments in email messages or instant messaging messages. That is why it is essential that you never open email attachments unless you know who it's from and you are expecting it.
Viruses can be disguised as attachments of funny images, greeting cards, or audio and video files.
Computer viruses also spread through downloads on the Internet. They can be hidden in illicit software or other files or programs you might download.
The Types Of Computer Viruses
1. Boot Sector Virus
2. File Infection Virus
3. Multipartite Virus
4. Network Virus
5. E-mail Virus
6. Macro Virus
Boot Sector Viruses
Viruses that aim at the boot sector of a hard drive are infecting a very crucial component of the boot process. The boot sector holds critical information that controls the hard drive and also the part of the operating program that is in charge of the whole boot process. These types of computer viruses go a long way toward the assurance they will be successful in their mission by absolutely loading into the system memory while the boot cycle is starting.
Unlike other viruses the boot virus does not affect files, instead it goes after the drive itself on which the virus is saved and this is part of the reason that it is no longer as big a threat as it used to be. Since the advent of cds and dvds and the drives that carry them it is not possible to infect the programs that they carry. In the days of floppy drives the virus could spread quite quickly from computer to computer via the disks but since it is not possible to infect a cd or dvd this virus has become almost a non threat. Another reason this types of computer viruses have become less common is that now operating systems stand guard over the boot sector and that makes it very hard for the virus to have any effect.
File Virus
File viruses are coded so that they will attach themselves to exe files, compressed files like zip files and driver files. The can be set into actions when the program they are attached to is started. Then after the virus is set into motion it will attach itself to other programs and system files and start along it's intended path for which it was written. So you see it is a two prong approach. First depending on the types of computer viruses it will duplicate and then go about its intended mission. The virus will search through the programs in the system and find places to infect with the code and then it will activate when that program is run next time. It will continue to duplicate until it is all over the computer and probably any computer that is attached to the original system.
Often these viruses will harbor special code that causes them to be activated when certain events take place. The event often is a date or some other trigger event that is easily defined on any computer system you may have.
Multipartite Viruses
That which has been termed the multipartite virus are the types of computer viruses that are both a file virus and a boot sector virus. They enter the computer via various sorts of media and then embed themselves in the system memory. They then go into the hard drive and infect the boot sector. Once installed in the boot sector these types of computer viruses infect executable files and spread themselves in the system.
This is another virus that has past its prime for various reasons but in times past these types of computer viruses were responsible for many infections because they combined characteristics of two different viruses into one.
Network Viruses
A virus that is especially made for networks is uniquely created to quickly spread throughout the local area network and generally across the internet as well. Most of the time is moves within shared resources like drives and folders. Once it finds entry into a system it will search for vulnerable computers in the network and likewise infect that system and do the same again and again always on the hunt for new vulnerable systems.
E-Mail Viruses
Most of the time a e-mail virus is one of those types of computer viruses that is generally a macro virus and it will multiply itself by seeking out the other contacts in a e-mail address book and then send itself to those addresses in hopes that they will activate the virus too. Thus it spreads over and over again exponentially. There are even times an email virus can spread by only previewing it in the mail client. One that was very successful in spreading worldwide was the ILOVEYOU virus and it was destructive too.
Macro Viruses
Macro viruses as the name implies, will infect files of programs that use macros in the program itself. The most common of these are the Microsoft Office files created in Excel spreadsheets, Word documents, Access databases, Powerpoint presentations and these type of files from AmiPro and Corel Draw and others.
These types of computer viruses are programmed using the language that the application understands and not in the language of the operating system thus they are operating in a way that is independent of the operating system so it can infect any kind of system be it Mac, PC or even Linux just as long as the computer is running the application that understands the macro virus. As the macro language has become more and more powerful the threat of these types of computer viruses has graduated to more critical types of computer viruses. These viruses have been around since 1995 and the first was found to infect Microsoft Word but now have moved to other programs and they number in the thousands.
Trojan Horse:
A trojan horse program has the appearance of having a useful and desired function. While it may advertise its activity after launching, this information is not apparent to the user beforehand. Secretly the program performs other, undesired functions. A Trojan Horse neither replicates nor copies itself, but causes damage or compromises the security of the computer. A Trojan Horse 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. The malicious functionality of a Trojan Horse may be anything undesirable for a computer user, including data destruction or compromising a system by providing a means for another computer to gain access, thus bypassing normal access controls.
Worms:
A worm is a program that makes and facilitates the distribution of copies of itself; for example, from one disk drive to another, or by copying itself using email or another transport mechanism. The worm may do damage and compromise the security of the computer. It may arrive via exploitation of a system vulnerability or by clicking on an infected e-mail.
Memory Resident Viruses:
Memory Resident Viruses reside in a computers volitale memory (RAM). They are initiated from a virus which runs on the computer and they stay in memory after it's initiating program closes.
Rootkit Virus:
A rootkit virus is an undetectable virus which attempts to allow someone to gain control of a computer system. The term rootkit comes from the linux administrator root user. These viruses are usually installed by trojans and are normally disguised as operating system files.
Polymorphic Viruses:
A polymorphic virus not only replicates itself by creating multiple files of itself, but it also changes it's digital signature every time it replicates. This makes it difficult for less sophisticated antivirus software to detect.
Logic Bombs/Time Bombs:
These are viruses which are programmed to initiate at a specific date or when a specific event occurs. Some examples are a virus which deletes your photos on Halloween, or a virus which deletes a database table if a certain employee gets fired.
Computer viruses are small software programs that are designed to spread from one computer to another and to interfere with computer operation.
- The first computer virus, called "Creeper", was written by Bob Thomas in 1971.
- The virus would display the message, "I'm a creeper, catch me if you can!" and messed with people's printers.
- It was written as a security test to see if a self-replicating program could be written (although technically it didn't self-replicate).
- To stop "Creeper", the first ANTI-virus was created. The anti-virus was called "Reaper".
- Rich Skrenta, who invented the "Elk Cloner" virus in 1981 for Apple 2, said that he did it as a "practical joke".
- Since then, people do it for a variety of reasons. Some are malicious and want to damage or destroy people's computers. Some do it as a joke. Some are trying to get at your personal financial data.
What do computer viruses do?
Many computer viruses are stopped before they can start, but there is still an ever growing concern as to what do computer viruses do and the list of common computer virus symptoms. A computer virus might corrupt or delete data on your computer, use your email program to spread itself to other computers, or even erase everything on your hard disk.Computer viruses are often spread by attachments in email messages or instant messaging messages. That is why it is essential that you never open email attachments unless you know who it's from and you are expecting it.
Viruses can be disguised as attachments of funny images, greeting cards, or audio and video files.
Computer viruses also spread through downloads on the Internet. They can be hidden in illicit software or other files or programs you might download.
The Types Of Computer Viruses
1. Boot Sector Virus
2. File Infection Virus
3. Multipartite Virus
4. Network Virus
5. E-mail Virus
6. Macro Virus
Boot Sector Viruses
Viruses that aim at the boot sector of a hard drive are infecting a very crucial component of the boot process. The boot sector holds critical information that controls the hard drive and also the part of the operating program that is in charge of the whole boot process. These types of computer viruses go a long way toward the assurance they will be successful in their mission by absolutely loading into the system memory while the boot cycle is starting.
Unlike other viruses the boot virus does not affect files, instead it goes after the drive itself on which the virus is saved and this is part of the reason that it is no longer as big a threat as it used to be. Since the advent of cds and dvds and the drives that carry them it is not possible to infect the programs that they carry. In the days of floppy drives the virus could spread quite quickly from computer to computer via the disks but since it is not possible to infect a cd or dvd this virus has become almost a non threat. Another reason this types of computer viruses have become less common is that now operating systems stand guard over the boot sector and that makes it very hard for the virus to have any effect.
File Virus
File viruses are coded so that they will attach themselves to exe files, compressed files like zip files and driver files. The can be set into actions when the program they are attached to is started. Then after the virus is set into motion it will attach itself to other programs and system files and start along it's intended path for which it was written. So you see it is a two prong approach. First depending on the types of computer viruses it will duplicate and then go about its intended mission. The virus will search through the programs in the system and find places to infect with the code and then it will activate when that program is run next time. It will continue to duplicate until it is all over the computer and probably any computer that is attached to the original system.
Often these viruses will harbor special code that causes them to be activated when certain events take place. The event often is a date or some other trigger event that is easily defined on any computer system you may have.
Multipartite Viruses
That which has been termed the multipartite virus are the types of computer viruses that are both a file virus and a boot sector virus. They enter the computer via various sorts of media and then embed themselves in the system memory. They then go into the hard drive and infect the boot sector. Once installed in the boot sector these types of computer viruses infect executable files and spread themselves in the system.
This is another virus that has past its prime for various reasons but in times past these types of computer viruses were responsible for many infections because they combined characteristics of two different viruses into one.
Network Viruses
A virus that is especially made for networks is uniquely created to quickly spread throughout the local area network and generally across the internet as well. Most of the time is moves within shared resources like drives and folders. Once it finds entry into a system it will search for vulnerable computers in the network and likewise infect that system and do the same again and again always on the hunt for new vulnerable systems.
E-Mail Viruses
Most of the time a e-mail virus is one of those types of computer viruses that is generally a macro virus and it will multiply itself by seeking out the other contacts in a e-mail address book and then send itself to those addresses in hopes that they will activate the virus too. Thus it spreads over and over again exponentially. There are even times an email virus can spread by only previewing it in the mail client. One that was very successful in spreading worldwide was the ILOVEYOU virus and it was destructive too.
Macro Viruses
Macro viruses as the name implies, will infect files of programs that use macros in the program itself. The most common of these are the Microsoft Office files created in Excel spreadsheets, Word documents, Access databases, Powerpoint presentations and these type of files from AmiPro and Corel Draw and others.
These types of computer viruses are programmed using the language that the application understands and not in the language of the operating system thus they are operating in a way that is independent of the operating system so it can infect any kind of system be it Mac, PC or even Linux just as long as the computer is running the application that understands the macro virus. As the macro language has become more and more powerful the threat of these types of computer viruses has graduated to more critical types of computer viruses. These viruses have been around since 1995 and the first was found to infect Microsoft Word but now have moved to other programs and they number in the thousands.
Trojan Horse:
A trojan horse program has the appearance of having a useful and desired function. While it may advertise its activity after launching, this information is not apparent to the user beforehand. Secretly the program performs other, undesired functions. A Trojan Horse neither replicates nor copies itself, but causes damage or compromises the security of the computer. A Trojan Horse 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. The malicious functionality of a Trojan Horse may be anything undesirable for a computer user, including data destruction or compromising a system by providing a means for another computer to gain access, thus bypassing normal access controls.
Worms:
A worm is a program that makes and facilitates the distribution of copies of itself; for example, from one disk drive to another, or by copying itself using email or another transport mechanism. The worm may do damage and compromise the security of the computer. It may arrive via exploitation of a system vulnerability or by clicking on an infected e-mail.
Memory Resident Viruses:
Memory Resident Viruses reside in a computers volitale memory (RAM). They are initiated from a virus which runs on the computer and they stay in memory after it's initiating program closes.
Rootkit Virus:
A rootkit virus is an undetectable virus which attempts to allow someone to gain control of a computer system. The term rootkit comes from the linux administrator root user. These viruses are usually installed by trojans and are normally disguised as operating system files.
Polymorphic Viruses:
A polymorphic virus not only replicates itself by creating multiple files of itself, but it also changes it's digital signature every time it replicates. This makes it difficult for less sophisticated antivirus software to detect.
Logic Bombs/Time Bombs:
These are viruses which are programmed to initiate at a specific date or when a specific event occurs. Some examples are a virus which deletes your photos on Halloween, or a virus which deletes a database table if a certain employee gets fired.
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