On Wikipedia, vandalism is editing the project in an intentionally disruptive or malicious manner. Vandalism includes any addition, removal, or modification that is intentionally humorous, nonsensical, a hoax, offensive, libelous or degrading in any way. Throughout its history, Wikipedia has struggled to maintain a balance between allowing the freedom of open editing and protecting the accuracy of its information when false information can be potentially damaging to its subjects. Vandalism is easy to commit on Wikipedia because anyone can edit the site, with the exception of protected pages (which, depending on the level of protection, can only be edited by users with certain privileges). Certain Wikipedia bots are capable of detecting and removing vandalism faster than any human editor could. It is not a criminal act to vandalize Wikipedia. However, it is against the site's terms of use to vandalize or otherwise cause disruption. Vandals are blocked from editing, and may also be further banned according to the terms of use. Vandalism can be committed by either guest editors (IP addresses) or those with registered accounts. To combat inappropriate user edits, Wikipedia has instated a protection policy, serving as a user-privilege merit system. For example, a semi-protected or fully protected page can be edited only by accounts that meet certain account age and activity thresholds or administrators respectively. Frequent targets of vandalism include articles on trending and controversial topics, celebrities, and current events. In some cases, people have been falsely reported as having died. This has notably happened to United States Senators Ted Kennedy and Robert Byrd, and American rapper Kanye West. There are various measures taken by Wikipedia to prevent or reduce the amount of vandalism. These include: Using Wikipedia's history functionality, which retains all prior versions of an article, restoring the article to the last version before the vandalism occurred; this is called reverting vandalism.