Computer Virus and its Types - Notes For Exams

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Computer Virus
  • A computer virus is a malware program which when executed, replicates itself into computer programs, data files, or the boot sector of the hard drive. 
  • It is a program designed to replicate itself into other files or programs stored on your device. 
  • Viruses can cause programs to operate incorrectly or corrupt a computer's momory. 
  • Viruses also access the private information of the user, corrupts data, spamming their contacts, or logging their keystrokes. 
  • The Creeper virus was first detected on ARPANET, the forerunner of the Internet, in the early 1970s.
Virus spreads through 
  1. E-mail attachments
  2. Portable devices such as CDs, DVDs, Pendrives, Memory Cards etc
  3. Websites containing malicious scripts 
  4. File downloads from Internet
Important Types of Virus
  1. Macro Virus - Macro virus harms the documents which use macros such as word processing and excel spreadsheet documents. A macro virus is written in macro language.
  2. Companion Virus – A virus that creates a new file with same existing filename.
  3. Virus hoax – A computer virus hoax is a message, can be a false e-mail warning the recipients to forward it to everyone they know.
  4. Computer prank – It is a prank related to either the software or the hardware of computers.
  5. WORM – A computer worm is a computer program that replicates itself in order to spread to other computers. It mostly uses a computer network to spread itself. Unlike a computer virus, it does not need to attach itself to an existing program.
  6. Trojan horse – A Trojan horse is a generally non-self-replicating type of code which when executed, causes loss or theft of data, and possible system harm.
Computer Virus and Its Types

  • Antivirus software is a computer software used to prevent, detect and remove malicious software from computer.
  • Antivirus software detects and removes computer viruses from the system. Antivirus software also provides protection from other computer threats as there is rapid increase of other kinds of malwares.
  • Now days, an antivirus protects the computer from malicious Browser Helper Objects (BHOs), browser hijackers, ransomware, keyloggers, backdoors, rootkits, trojan horses, worms, malicious LSPs, dialers, fraud tools, adware, and spyware.
  • Examples - Norton, AVG, Optimo, AV, Mcafee, Avira, Bitdefender, Pandasecurity, Eset, QuickHeal, Kaspersky, Immunet and etc.
Important Computer Security Threats
  1. Phishing – The act of acquiring private or sensitive data from personal computers for use in fraudulent activities. Phishing is usually done by sending emails that seem to appear to come from credible sources (however, they are in no way affiliated with the actual source/company), which require users to put in personal data such as a credit card number or social security number. This information is then transmitted to the hacker and utilized to commit acts of fraud. 
  2. Spam – Spamming is sending unsolicited messages, especially advertising, as well as sending bulk messages on the same site or through an e-mail.
  3. Malware – Malware disrupts computer operation, gather sensitive information, or gain access to private computer systems without the user’s knowledge.
  4. Adware - It is a software package which automatically starts advertisement.
  5. Spyware – Spyware is software that is secretly installed on a computer without the user’s consent. It monitors user activity or interferes with user control over a personal computer.
  6. Firewall – A firewall is a network security system which controls the incoming and outgoing network traffic based on a set of rules. A firewall establishes an obstacle between a trusted, secure internal network and another network. Firewalls exist both as a software solution and as a hardware appliance.
  7. SPIM - SPIM is spam sent via instant messaging systems such as Yahoo! Messenger, MSN Messenger and ICQ.
  8. SPIT - SPIT is Spam over Internet Telephony. These are unwanted, automatically-dialed, pre-recorded phone calls using Voice over Internet Protocol (VoIP).
  9. Spoofing - Spoofing is an attack in which a person or program masquerades as another. A common tactic is to spoof a URL or website (see phishing).
  10. Pharming - Pharming is an attack in which a hacker attempts to redirect a website's traffic to another website. Pharming can be conducted either by changing the hosts file on a victim’s computer or by exploitation of a vulnerability in DNS server software. 
  11. Keylogger - A keylogger is a software program that is installed on a computer, often by a Trojan horse or virus. Keyloggers capture and record user keystrokes. The data captured is then transmitted to a remote computer.
  12. Blended Threat - A blended threat is a threat that combines different malicious components, such as a worm, a Trojan horse and a virus. In this way, a blended threat uses multiple techniques to attack and propagate itself.