Malvertising
Websites or web publishers unknowingly incorporate a corrupted or malicious advertisement into their page. Computers can become infected pre-click and post click. It is a misconception that infection only happens when visitors begin clicking on a malvertisement. "Examples of pre-click malware include being embedded in main scripts of the page or drive-by-downloads. Malware can also auto-run, as in the case of auto redirects, where the user is automatically taken to a different site, which could be malicious. Malware can also be found in the delivery of an ad – where a clean ad that has no malware pre or post click (in its build and design) can still be infected whilst being called. Malicious code can hide undetected and the user has no idea what's coming their way. A post-click malvertisement example: "the user clicks on the ad to visit the advertised site, and instead is directly infected or redirected to a malicious site. These sites trick users into copying viruses or spyware usually disguised as Flash files, which are very popular on the web." Redirection is often built into online advertising, and this spread of malware is often successful because users expect a redirection to happen when clicking on an advertisement. A redirection that is taking place only needs to be co-opted in order to infect a user's computer.
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.