Recently, systems supporting flexible security models start to appear (e.g., SELinux, Trusted Solaris, TrustedBSD, etc.) Security Policy Model A security policy model is a succinct statement of the protection properties that a system, or generic type of system, must have.ΔΆ CIS/CSE 643: Computer Security (Syracuse University) MAC: 2 2 Multilevel Security 2.1 Security Levels People and information are classified into different levels of trust and sensitivity. Traditional MAC mechanisms have been tightly coupled to a few security models. Examples: The law allows a court to access driving records without the owners permission. MAC: Mandatory Access Control Definition: A system-wide policy decrees who is allowed to have access individual user cannot alter that access. Flawed software: Similarly to the previous item, flawed software can be instructed by attackers to change its DAC policies. Malicious software: DAC policies can be easily changed by owner, so a malicious program (e.g., a downloaded untrustworthy program) running by the owner can change DAC policies on behalf of the owner. This has been a major concern for military. Information flow: information can be copied from one object to another, so access to a copy is possible even if the owner of the original does not provide access to the original copy. Therefore, if there is a global policy, DAC has trouble to ensure consistency. Limitation of DAC: Global policy: DAC let users to decide the access control policies on their data, regardless of whether those policies are consistent with the global policies. Strength of DAC: Flexibility: a key reason why it is widely known and implemented in mainstream operating systems. DAC is widely implemented in most operating systems, and we are quite familiar with it. Relies on the object owner to control access. 1 CIS/CSE 643: Computer Security (Syracuse University) MAC: 1 1 Why need MAC DAC: Discretionary Access Control Mandatory Access Control Definition: An individual user can set an access control mechanism to allow or deny access to an object.
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