Malware
A specific component of anti-virus and anti-malware software, commonly referred to as an on-access or real-time scanner, hooks deep into the operating system's core or kernel and functions in a manner similar to how certain malware itself would attempt to operate, though with the user's informed permission for protecting the system. Any time the operating system accesses a file, the on-access scanner checks if the file is a 'legitimate' file or not. If the file is identified as malware by the scanner, the access operation will be stopped, the file will be dealt with by the scanner in a pre-defined way (how the anti-virus program was configured during/post installation), and the user will be notified. This may have a considerable performance impact on the operating system, though the degree of impact is dependent on how well the scanner was programmed. The goal is to stop any operations the malware may attempt on the system before they occur, including activities which might exploit bugs or trigger unexpected operating system behavior.
Vandalism
Cybervandalism is vandalism on the internet. For example, vandalism on Wikipedia involves adding questionable content, removing content, or changing content in order to make it questionable, generally with the objective of harming Wikipedia's reputation. Forms of online vandalism have been recorded, the most common of which is website defacement. Vandalism on web maps has been called "cartographic vandalism". Another form of cybervandalism is creation of malware, such as viruses, Trojan horses, and spyware, which can destroy computers, and in some cases even steal money from the computer owners, wherein the malware creator blackmails the owner to pay them money or give out their credit card number or else they won't get the use of their computer back. Some even go as far as making a time limit where if the owner doesn't pay or give personal information within a certain time, the malware permanently destroys the computer.