Classified information is material that a government body deems to be sensitive information that must be protected. Access is restricted by law or regulation to particular groups of people with the necessary security clearance and need to know, and intentionally mishandling of the material can incur criminal penalties. A formal security clearance is required to view or handle classified documents or to access classified data. The clearance process requires a satisfactory background investigation. Documents and other information must be properly marked "by the author" with one of several (hierarchical) levels of sensitivity—e. g. restricted, confidential, secret and top secret. The choice of level is based on an impact assessment; governments have their own criteria, which include how to determine the classification of an information asset, and rules on how to protect information classified at each level. This often includes security clearances for personnel handling the information. Although "classified information" refers to the formal categorization and marking of material by level of sensitivity, it has also developed a sense synonymous with "censored" in US English. A distinction is often made between formal security classification and privacy markings such as "commercial in confidence". Classifications can be used with additional keywords that give more detailed instructions on how data should be used or protected.