Computer viruses - definition and types

A computer virus is a program that multiplies and spreads by attacking other programs. This is done without the knowledge and permission of the user. When the infected program is launched, the virus performs an action that may be:

     A. Irritant - display a message on a certain date, slow system performance, change the screen resolution, the issue of strange sounds and more.

     2. Fatal - deleting files, identity theft, system crash, etc...

     Malware spread through files attached to emails, via P2P, LAN, WAN networks with links to infected sites, files and more.

     Not all malware are viruses. Here are some more familiar:

Virus's attack the computer

     A. Worms - A worm is a program to multiply, but not infect other programs. It infects computers whether they are part of a network or not. The worm is copied to and from floppy discs, CD, DVD, Blue-Ray and "sticks" as well as on different partitions on the hard disk. If an infected computer is part of the network, it can infect other computers on it. Worms often steal and destroy data and distributed primarily through the Internet.

     2. Trojan horses - A Trojan horse is a malicious program that is hidden in a harmless one. When this program starts up and runs the Trojan horse to perform a certain task. Trojans can steal personal information (passwords, user names); delete files, formatted hard disk, etc...

     3. Droppers (containers) - "container" is a program which is designed to overcome antivirus - usually through encryption, which prevents the antivirus program to detect. It lurks in your computer to the occurrence of an event and then it infected with the virus, which contains, i.e. it acts as a "container for viruses." Hence the name of her

     4. Bombs - Bomb harmful script or program that is triggered when certain conditions. Some bombs are activated on certain dates using the system clock. For example, the bomb can be programmed to delete all *. Doc files of the New Year. Another bomb can not wait to be open for 17 roads and then be activated.

     Viruses can spread through "containers" or proliferate as worms. Can be attacked by Trojans by attaching to other programs. Therefore, they are the most dangerous.

     Viruses are divided into several types:

A.    Boot sector viruses - This type of virus infects the boot record of HDD. At first he moved or overwrites the original boot entry by replacing it with an infected. Move the original recording is recorded in a sector virus marked as damaged, not to use more (anti-virus applications will not scan because it is damaged). To become infected with this virus you must start your computer from an infected floppy disk, CD, DVD, Blue-Ray, flash drive or other data carrier. When checking the boot sector virus fool antivirus directs it to scan clean up contaminated instead.

2. File viruses - This is one of the most common types of viruses. These viruses search for files with certain extension (usually executable files as *. Com and *. Exe) and infect them. When the program is opened, the virus started infecting more files.

     3. Macro viruses - These viruses use special programs and files supported by them to multiply. Macro viruses usually infect files in MS Excel, but can infect other files that use programming language. They do not infect programs. When you open an infected document, the virus spreads to other documents. Macro viruses can cause severe damage to the documents contained in the infected computer. Unpleasant that can be distributed between different operating systems.

     4. Polymorphic viruses - These viruses change their code with each infection, making them difficult to detect.

     5. Multi-polymorphic viruses - they infect the boot records and executables. These viruses can combine the advantages of stealth and polymorphic viruses.

     6. Stealth viruses - Easy to avoid antivirus scans (through encryption of program code or to hide in memory) as they fail to detect changes in files infected by them, giving them the same old data files. This makes them difficult to detect.

     7. Hacker Tools - Used for:

          A) Establishment of viruses, worms and Trojan horses;

          B) Encryption of viruses, making them harder to detect;

          C) Creating etc. "Joke programs", which are annoying but harmless and cause a change of screen resolution, window opening, and vocalization.