What counts as copyrighted material?
Your academic publication? Your grandpa's letters? An audio recording of your best friend? Technically, all of these items are subject to copyright.
Even if an individual has not filed for copyright protection, by default the copyright lies with the creator or originator of the content. Within some companies or institutions, an individual's work as an employee of the institution is considered the property of the institution rather than the individual. This is generally stipulated in an individual's contract of employment or in an official policy statement. Most published material will also be filed with the copyright office, making protection of the author/creator's rights more easily enforceable in a court of law.
Copyright does expire and is subject to certain exceptions. The most recent material that will have fallen out of copyright was published in 1923. The most recent exception to copyright falls under The Marrakesh Treaty.