Once you’ve started using your computer, viruses can start working on your computer. The computer virus is one of those programs you don’t want that usually gets sent to you by people through email. But just as there are medicines for common colds, there are also remedies for computer viruses. Your computer’s anti-biotic shots take the form of AntiVirus programs, which you install to combat the viruses. The Mcaffee and Norton AntiVirus are two commonly used anti-virus programs.
How does a computer get infected by a virus? Typically, virus infections spread when somebody inserts a disk containing an infected program into a computer, and then starts the infected program. You might also get a virus by downloading an infected program from the Internet. Either way, starting the infected program causes the virus to start copying itself. The virus attaches itself to other programs and soon infects much or all of the software in your computer.
Although many viruses are best categorized as nuisances or pranks, all consume system memory and slow the computer’s processing speed, and some damage data. Viruses that attach themselves to a program file are called file infectors. When the program is executed, the virus spreads to other programs on the user’s hard disk. Most viruses are file infectors. A second and far more serious type of virus is called a boot sector virus. A boot sector virus propagates by means of infected program, but it installs itself at the beginning of a hard drive, where code is stored that automatically executes every time you start your computer. This virus may lead to the destruction of all the data stored on the hard drive. Most recently, a third type of virus, called a macro virus, has appeared. Macro viruses take advantage of the automatic command execution capabilities (called macros) of productivity software, such as word processing and spreadsheet programs. What’s scary about macro viruses is that they infect data files containing the data created with an application program such as Microsoft Word.
A worm resembles a computer virus in that it can spread from one computer to another. Unlike a virus, however, a worm can propagate over a computer network, and it does not require an unsuspecting user to execute a program or macro file. It takes control of affected computers and uses their resources to attack other network-connected systems.
A Trojan horse is disguised as a useful program, but it contains hidden instructions to perform a malicious task instead. Sometimes a Trojan horse is disguised as a game or a utility program that users will find appealing. Then, when the users begin running the game, they discover that they have loaded another animal entirely. A Trojan horse may erase the data on the hard disk or cause other damage.
Payload is the destructive event or prank the program is intended to deliver. A computer infected by a virus, worm or trojan horse often has one or more of the following symptoms.
Some companies and organizations use honeypots so they can analyze an attack being perpetrated. A honeypot is a vulnerable computer that is set up to entice an intruder to break into it. These computers, which appear real to the intruder , actually are separated safely from the company or organization's network. Honeypots allow the company or organization to learn how intruders are exploiting their network and also attempt to catch perpetrators who have been doing damage elsewhere on their network. Large Web hosting companies, such as Yahoo! and AT&T, and law enforcement agencies frequently use honeypots.
Botnet is a term derived from the idea of bot networks. In its most basic form, a bot is simply an automated computer program, or robor. In the context of botnets, bots refer to computers that are able to be controlled by one , or many, outside sources. An attacker usually gains control by infecting the computers with a virus or other malicious code that gives the attacker access. Your computer may be part of a botnet even though it appears to be operating normally. Botnets are often used to conduct a range of activities, from distributing spam and viruses to conducting denial-of-service attacks.
Network spoofing is an ingenious way for an intruder to gain access. The intruder sets up as program that impersonates the sign-on routine for another system. When you attempt to login to the system, the intruder’s program collects your password, then returns a message that the system is unavailable. Users usually defeat this by regularly changing their passwords so that the collected passwords may no longer work by the time the intruder tries to gain access to your system.
A denial of service attack, or DoS attack, is an assault whose purpose is to disrupt computer access to an Internet service such as the Web or e-mail. Perpetrators carry out a DoS attack in a variety of ways. For example, they may use an unsuspecting computer to send an influx of confusing data messages or useless traffic to a computer network. The victim computer network eventually jams, blocking legitimate visitors from accessing the network.
A more devastating type of DoS attack is the DDoS (distributed DoS)attack, in which multiple unsuspecting computers are used to attack multiple computer networks. DDoS attacks have been able to stop operations temporarily at numerous Web sites, including powerhouses such as Yahoo!, Amazon.com, eBay, and CNN.com.
A backdoor is a secret decoding mechanism that enables investigators to decrypt messages without first having to obtain a private key.
A firewall is hardware and/or software that protects a network’s resources from intrusion by users on another network such as the Internet. All networked and online computer users should implement a firewall solution.
Companies use firewalls to protect network resources from outsiders and to restrict employees’ access to sensitive data such as payroll or personnel records. Businesses can implement a firewall solution themselves or outsource their needs to a company specializing in providing firewall protection.
References:
Computer Viruses and Data Protection, Ralf Burger
Computer Viruses and Data Protection, Ralf Burger
Introduction to Information Technology, Bryan Pfaffenberger
Computer Essentials, STI, Inc.
http://www.us-cert.gov/cas/tips/ST06-001.html
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