The First Computer Virus Elk Cloner is one of the first known microcomputerviruses that spread "in the wild," i.e., outside thecomputer system or lab in which it was written. It was written around 1982 by a 15-year-old highschool student named Rich Skrenta for Apple IIsystems.
Types of virusesBoot virusesProgram virusesMultipartite virusesStealth virusesPolymorphic virusesMacro Viruses
Infect floppy disk boot records or master bootrecords in hard disks. They replace the boot record program copying itelsewhere on the disk or overwriting it. Boot viruses load into memory if the computertries to read the disk while it is booting.Examples: Form, Disk Killer, Michelangelo, and Stone virus
infect executable program files, such as thosewith extensions like.BIN, .COM, .EXE, .OVL, .DRV (driver) and.SYS (device driver). These programs are loaded in memory duringexecution, taking the virus with them. The virus becomes active in memory, makingcopies of itself and infecting files on disk.Examples: Sunday, Cascade
A hybrid of Boot and Program viruses They infect program files and when theinfected program is executed, these virusesinfect the boot record. When you boot the computer next time thevirus from the boot record loads in memoryand then starts infecting other program fileson disk.Examples: Invader, Flip, andTequila
These viruses use certain techniques to avoiddetection They may either redirect the disk head toread another sector instead of the one inwhich they reside or they may alter thereading of the infected file’s size shown in thedirectory listing.Examples: Frodo, Joshi,Whale
A virus that can encrypt its code in differentways so that it appears differently in eachinfection. These viruses are more difficult to detect.Examples: Involuntary, Stimulate, Cascade, Phoenix, Evil, Proud, Virus 101Examples: Involuntary, Stimulate, Cascade, Phoenix, Evil, Proud, Virus 101Examples: Involuntary, Stimulate, Cascade, Phoenix, Evil, Proud, Virus 101Examples: Involuntary, Stimulate, Cascade, Phoenix, Evil, Proud, Virus 101Examples: Involuntary, Stimulate, Cascade, Phoenix, Evil, Proud, Virus 101Examples: Involuntary, Stimulate, Cascade, Phoenix, Evil,Proud,Virus 101
A macro virus is a new type of computer virusthat infects the macros within a document ortemplate. When you open a word processing orspreadsheet document, the macro virus isactivated and it infects the Normal template(Normal.dot)-a general purpose file thatstores default document formatting settings.
Every document you open refers to theNormal template, and hence gets infectedwith the macro virus. Since this virus attaches itself todocuments, the infection can spread if suchdocuments are opened on other computers.Examples: DMV, Nuclear,Word Concept.
Adware or advertising-supported softwareis any software package which automaticallyplays, displays, or downloads advertisementsto a computer after the software is installedon it or while the application is being used.Some types of adware are also spyware andcan be classified as privacy-invasive software.
Malware, short for malicious software, issoftware designed to infiltrate a computerwithout the owners informed consent. Theexpression is a general term used bycomputer professionals to mean a variety offorms of hostile, intrusive, or annoyingsoftware or program code. The term"computer virus" is sometimes used as acatch-all phrase to include all types ofmalware, including true viruses.
Once a malicious program is installed on a system, it isessential that it stay concealed, to avoid detection anddisinfection.The same is true when a human attackerbreaks into a computer directly.Techniques known asrootkits allow this concealment, by modifying the hostoperating system so that the malware is hidden from theuser. Rootkits can prevent a malicious process from beingvisible in the systems list of processes, or keep its filesfrom being read. Originally, a rootkit was a set of toolsinstalled by a human attacker on a Unix system where theattacker had gained administrator (root) access.Today, the term is used more generally for concealmentroutines in a malicious program.
A backdoor is a method of bypassing normalauthentication procedures.Once a system hasbeen compromised one or more backdoors maybe installed in order to allow easier access in thefuture. Backdoors may also be installed prior tomalicious software, to allow attackers entry Crackers typically use backdoors to secureremote access to a computer, while attemptingto remain hidden from casual inspection.
Spam is the abuse of electronic messaging systems(including most broadcast media, digital deliverysystems) to send unsolicited bulk messagesindiscriminately. While the most widely recognizedform of spam is e-mail spam E-mail spam, known as unsolicited bulk Email (UBE),junk mail, or unsolicited commercial email (UCE), isthe practice of sending unwanted e-mail messages,frequently with commercial content, in largequantities to an indiscriminate set of recipients.
Spyware is a type of malware that is installed oncomputers and that collects information aboutusers without their knowledge. The presence ofspyware is typically hidden from the user.Typically, spyware is secretly installed on theusers personal computer.Sometimes, however, spywares such askeyloggers are installed by the owner of ashared, corporate, or public computer on purposein order to secretly monitor other users.