Network abuse is the use of a computer network for purposes prohibited by the network's acceptable use policy. It usually includes internet crime and other malicious uses, such as use that may interfere with other users' ability to access network services. It is not uncommon for networks to prohibit the access or transmission of obscene, profane, or controversial material, especially considering employer and school networks. Some networks employ content filters or firewalls designed to block objectionable activity. Vandalism to wikis such as this one is considered malicious activity by many network operators. Most network operators maintain a specific email address or other contact for reporting network abuse.