Question: Describe the following types of attacks.

a) Computer virus
A computer virus is a type of malware that, when executed, replicates by inserting copies of itself (possibly modified) into other computer programs, data files, or the boot sector of the hard drive; when this replication succeeds, the affected areas are then said to be "infected". b) Worm
A computer worm is a standalone malware computer program that replicates itself in order to spread to other computers.[1] Often, it uses a computer network to spread itself, relying on security failures on the target computer to access it. Unlike a computer virus, it does not need to attach itself to an existing program.[2] Worms almost always cause at least some harm to the network, even if only by consuming bandwidth, whereas viruses almost always corrupt or modify files on a targeted computer. c) Trojan horse
A Trojan horse, or Trojan, in computing is a non-self-replicating type of malware program containing malicious code that, when executed, carries out actions determined by the nature of the Trojan, typically causing loss or theft of data, and possible system harm. A Trojan often acts as a backdoor, contacting a controller which can then have unauthorized access to the affected computer.[6] The Trojan and backdoors are not themselves easily detectable, but if they carry out significant computing or communications activity may cause the computer to run noticeably slowly. d) DOS
DoS ( denial-of-service attack )attack is a malicious attempt by a single person or a group of people to cause the victim, site, or node to deny service to its customers. DoS ,a type of attack on a network that is designed to bring the network to its knees by flooding it with useless traffic. Many DoS attacks, such as the Ping of Death and Teardrop attacks, exploit limitations in the TCP/IP protocols. For all