A black hat is a person who compromises the security of a computer system without permission from an authorized party, typically with malicious intent. The term white hat is used for a person who is ethically opposed to the abuse of computer systems, but is frequently no less skilled. In recent years the terms white hat and black hat have been applied to the Search Engine Optimization (SEO) industry. Black hat SEO tactics, also called spamdexing, attempt unfairly to redirect search results to particular target pages, whereas white hat methods are generally approved by the search engines. A grey hat refers to a skilled hacker who sometimes acts illegally, sometimes in good will, and sometimes not.