Integrity of information means that information remains unaltered by unauthorized users. Misuse may involve legitimate users such as, insiders performing unauthorized operations or intruders. A legitimate user may perform an incorrect, or unauthorized operational function because of several factors, including the possibility that the level of access permission granted to the user is higher than what the user needs. An attacker might be able to alter data because:
An intruder masquerades as a legitimate user and accesses an operations port of the system. Then, the intruder can perform such operations as:
Disclosing confidential data
Causing service deterioration by modifying the system software
Crashing the system
Removing all traces of the intrusion (for example, modifying the security log)
At certain times the system becomes vulnerable because it is not in a secure state. For example:
After a system restart or during a disaster recovery, the old security features may have been reset to insecure settings, and new features might not yet be activated. (For example, all old passwords might have reverted to the default system-password, even though new passwords are not yet assigned.)
At the time of installation the system may be vulnerable until the default security features have been replaced.