Viruses and worms can affect your computer and programs in a variety of ways. The least harmful is a slowing down of your computer in terms of speed (as minimal as it might be).
Many computer- viruses hold programming errors which can at times lead to fatal results. Although mostly unintentional, these errors can destroy data by means of wrongs infections. At times complete data losses have been the consequence.
Some virues are written especially for the destruction of data. This can result in the deletion of single data – at times also in the formatting of entire hard drives. Such kind of Payload is usually associated by most users. Since the hard drive constitutes the habitat of viruses, they ,commit suicide‘ while accomplishing their mission.
Overwriting viruses are the most simple form of viruses. Their destructive force is the most powerful, but they are also the easiest to detect. When an infected program is being run, viruses are searching for new data they can infect. Once found, the parts of – or at times – the entire data will be overwritten (usually only the beginning). By doing so, the host and its functionality will irreversibly be damaged which is why the infection becomes immediately visible.
Retroviruses aim at deactivating virus protection programs in addition to personal firewalls. They are considered as especially dangerous, since they not only protect themselves of being detected, but also assist other malware to remain undetected.
Most trojan horses are being used for secretly installing other malware. This malware runs independently on your computer. It cannot be deactivated, even if the trojan is being detected or deleted. More and more frequently, trojans are being used for professional the conduct of internet crimes:
Economic damage starts with any confinement with regards to your working routine and procedure, not talking about the necessity of having to acquire new hardware components, programs, etc.. However, a number of viruses have been written to especially cause financial damage.
In 1998, for instance, a virus was detected which attacked Excel-data by using a very vicious malware: the virus would look for any random document containing unprotected cells with numeric data every time when excel was being quit. In these cells, 1 % of the data were randomly modified – altering the respective value by + to – 5 %. As these changes were rather insignificant, it took weeks and months for the errors to become visible. Entire balance sheets of a number of big companies became entirely useless.