Viruses and anti-virus software
Posted by The Bridge
Definition:
A computer virus is a self-propagating computer programme that infiltrates into other computer programmes. These programmes are outside the control of the user, changes the status of the hardware, operating system or the software. The classification as a virus is covered by the dissemination and disinfection function.
Difference between virus and worm:
Worms and viruses spread to both computer systems, but with completely different concepts and techniques. Viruses spread by themselves are copied in not infected files and then it waits until the file is executed. Infectable files are: programme files, programme libraries, scripts, documents, or other executable content. The spreading to new systems is done by copying an infected file.
The worm, however does not wait until it opens, but is actively trying to penetrate into new systems. It uses security problems on the target system. Most worms hidden in an inconspicuous place on the system with an inconspicuous name changed the target system so that the worm is activated during system startup.
The way of spreading early and today:
Before, the main way of spreading was through removable media such as floppy disks. Today it is through the network of computers.
Vulnerability of different operating systems:
Principally all operating systems that allow programmes to manipulate other files are susceptible. The rights of users can limit how far a virus can spread on the system. Operating systems without any rights have the highest risk to get a virus, if the user works as an administrator.
If a user works with a user account and limited rights, a virus can spread only to files, for which the user has the rights to change. As Windows systems have the widest distribution on PCs, they are the main target of virus writers.
Anti-virus with firewall and anti-viral programmes:
Firewalls have no effect on viruses. Anti-virus programmes only protect against known viruses, so it is important that the user updates regularly. Viruses of the next generation can almost be detected by antiviral programmes. These programmes scan the system memory. You have the hard drive for malicious programmes. Antivirus programmes never offer complete protection because the detection of the virus is very difficult and thus the detection rate of known viruses is not 100%. The viruses are often only discovered after the infection and then not removed just like that. If a virus is suspected to be under suspicion, the related file will be deleted or moved into quarantine. On the computer programmes should never be installed to work simultaneously, as this leads to malfunction of the PC and often false virus finds. To delete an infected file mostly leads to serious system failures, because often files that the operating system needs have to be deleted. In principle, occasionally, but regularly, the entire PC should be tested and with the help of the new virus database older, previously unrecognized virus files will be detected before they cause damage.
Different viruses
Selfsave Virus: There are five different species as to protect viruses.
Stealth Virus: This virus protects itself with a special trick. This type of virus catches system calls, that means the virus shows us the file size before infection.
Encoded Viruses: This kind of virus encodes itself. The key can vary with each infection. It is to prevent the antivirus programme simply to find certain number sequences in data.
Polymorphic viruses: This kind of virus changes its shape from generation to generation, sometimes completely, often in combination with a variable encoding. But a part of the virus must exist unencoded, to assist in the execution to decode the rest.
Metamorphic Viruses: This computer virus is almost like the polymorphic virus, but it changes not only its shape, but changes its version to the meta-language (Thus the name).
Retroviruses: Retroviruses are totally focused on anti-virus programmes and personal firewalls programmed to disable them.
Potential damage:
Computer viruses are dreaded because they have the call to destroy all files. But this is true only in very few cases. Most PC viruses are trying to spread themselves far.
Harmless effects:
The properties of each virus are stolen from computer time and memory. As it spreads itself, it is using the processor and hard drives. But viruses are usually written so that the system does not pose significant adverse effects, so that the user does not recognize it. The size of current hard drive is no longer on.
Accidental damage - programming error:
Many viruses contain errors that can lead to fatal consequences. Nevertheless these errors are unintentional but can destroy all data at the hard drives.
Data destruction:
At an infection of data to be included in files to manipulate and possibly destroyed. Very few viruses have been written for the destruction of data specifically. They can delete individual data or the hard drive. That is the idea of all kinds of viruses. There is the memory of the “living space” of the virus, however, they are usually destroying themselves with these actions.
Structure of viruses:
Viruses have many different forms, hence not all viruses are the same:
- Decryption routine: This part provides for encrypted viruses that encoded files will be brought to execution again. Not all viruses have this part.
- Multiplication part: Provides the multiplication of viruses, any virus has these parts.
- Recognition part: Here is tested if the infection of a programme or system area is already done. Each programme has only one infected host.
- Damage part: Very few viruses have this part and this part is the reason for the fear of many computer viruses.
- Condition part: This part is here for the damage to be exported and is usually included in the damage part.
- Simulation part: This part is present in complex viruses only. The virus is then encoded and placed in another form. This part is for the protection of the virus prior to the recognition, but there is only a small number of viruses that can not be fully recognized.
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