Computer Network Fundamentals. Physical layer. Data Link layer. Network layer. Transport layer. Application layer.
Network Security. Computer Network Quizes. Table of Contents. Improve Article. Save Article. Like Article. A virus is a fragment of code embedded in a legitimate program.
Viruses are self-replicating and are designed to infect other programs. They can wreak havoc in a system by modifying or destroying files causing system crashes and program malfunctions. On reaching the target machine a virus dropper usually a trojan horse inserts the virus into the system.
For more details, refer to this. Various types of viruses: File Virus: This type of virus infects the system by appending itself to the end of a file. It changes the start of a program so that the control jumps to its code. After the execution of its code, the control returns back to the main program. Its execution is not even noticed. Cyber crimes disrupt business and government operations and cause reputational harm. Cyber crime takes many different forms.
Criminals who infiltrate computers and networks have developed a variety of malicious software and social engineering techniques used individually or in combination when use in committing different types of cyber crime.
A few of the most common cyber crimes are described below. Criminal hacking is the act of gaining unauthorized access to data in a computer or network. Exploiting weaknesses in these systems, hackers steal data ranging from personal information and corporate secrets to government intelligence.
Hackers also infiltrate networks to disrupt operations of companies and governments. Computer and network intrusions cost billions of dollars annually, according to the FBI. Malware, or malicious software, refers to any code designed to interfere with a computer's normal functioning or commit a cyber crime.
Common types of malware include viruses, worms, trojans, and various hybrid programs as well as adware, spyware, and ransomware. Ransomware attacks are growing in volume and sophistication, the FBI reports.
Locking valuable digital files and demanding a ransom for their release, ransomware attacks are commonly executed using a trojan — malware that disguises its true intent. Ransomware typically infiltrates via email, luring a user to click on an attachment or visit a website that infects their computer with malicious code. Common ransomware targets include hospitals, schools, state and local governments, law enforcement agencies, and businesses.
Ransomware also targets individual users, holding personal information, photos, or other records. Not all identity thefts are a result of cyber attacks, but malware such as trojans and spyware are often used to steal personal information. A common method for perpetrating identity theft, phishing refers to a method used by cyber criminals to obtain confidential information using emails or texts.
Scammers pose as a trusted source often a bank or well-known company and trick recipients into providing personal information, such as account passwords and social security numbers. Phishing messages often use a story—for example, a claim that the sender has noticed suspicious activity with an account—to entice recipients to click a link or open an attachment. Social engineering is the psychological manipulation of people into performing actions or divulging confidential information.
Cyber criminals use social engineering to commit fraud online. Platforms such as online dating sites provide opportunities to initiate conversations with potential victims. Once the criminal establishes a relationship with the target and gains their trust, the criminal asks for money or information.
Social engineering techniques are often combined with technology elements. Macro viruses target applications and software that contain macros. These viruses can carry out series of operations affecting the performance of the program or software.
A, and Relax. Directory viruses change file paths. When you run programs and software that are infected with directory viruses, the virus program also runs in the background. Further, it may be difficult for you to locate the original app or software once infected with directory viruses. Polymorphic viruses use a special method of encoding or encryption every time they infect a system. With this, antivirus software finds it hard to locate then using signature searches.
They are also capable of replicating easily. This virus also infects executable files or programs. When you run these programs, the file infector virus is activated as well which can slow down the program and produce other damaging effects.
A large block of existing viruses belongs to this category. This type of virus uses encrypted malicious codes which make antivirus software hard to detect them. They can only be detected when they decrypt themselves during replication.
In order to carry out damages, the file or folder being accompanied by companion viruses should be opened or run. Some examples of companion viruses include Terrax. These viruses replicate through shared resources, including drives and folders. When network viruses enter a computer, they look for their potential prey. Nonresident viruses replicate through modules. When the module is executed, it will select one or more files to infect. Stealth viruses trick antivirus software by appearing like they are real files or programs and by intercepting its requests to the OS.
Some antivirus software cannot detect them. Sometimes, it temporarily removes itself from the system without deletion. Sparse infectors use different techniques to minimize its detection.
For example, they may only want to infect a program every tenth execution. Because they are occasional infectors, antivirus software has a hard time detecting them.
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