is short for "malicious software." It is a term that means a variety of forms of hostile, intrusive, or annoying software or program code. It is designed to infiltrate or damage a Computer System without the owner's informed consent.
Malicious little programs or scripts that can create files, move files, erase files, consume your computer's memory, and cause your computer not to function correctly or to crash completely. Some viruses can duplicate themselves, attach themselves to programs, and travel across networks.
They can self-modify or change over time as they copy themselves. Viruses only spread across multiple computers if an uninfected computer is connected to a network, or if the computer gets connected to infected media such as a USB drive or a CD.
A self-replicating computer program. It uses a network to send copies of itself to other computers on the network, and it may do so without any user intervention. Unlike a virus, it does not need to attach itself to an existing program. Worms almost always cause at least some harm to the network, if only by consuming bandwidth, whereas viruses almost always corrupt or devour files on a targeted computer.
3. Trojan Horse—
This type of malware comes hidden inside another program. They are often placed inside music, games, pictures, or anything else that someone might download onto their PC.Once you download the Trojan, it opens a back door that allows hackers unauthorized access to your machine. The criminals can save their files on your computer, watch your screen, take information, and completely control the computer.
A rootkit is a program designed to hide files, processes, or Windows Registry entries. Rootkits are not malware; they are the programs that help hide the malware. The rootkit usually comes bundled with malicious software including Trojans, viruses, worms, keyloggers, sniffers, botnets, etc.
Many rootkits can hide large numbers of files, enabling a hacker to invisibly store his files on your computer. Once the rootkit is installed, hackers can take control of your computer and use it for many illegal activities. They can send huge amounts of data to a website causing it to close down, send out spam, and store pirated movies, music, and software on your system. They can obtain your credit card information, and perform many other illegal activities, all of which hide the hacker's identity and make it seem as though the victim's computer is the source of the crime.
However, rootkits can be used legally by law enforcement, parents, and employers who want to monitor and check up on criminals, children, and employees. Spector Pro and eBlaster are two such programs. Though legal if used as suggested, these programs operate invisibly, like rootkits, and do not show up as an icon, do not appear in the Windows system tray, and do not appear in the Windows task list.