(ISC)2 CISSP Certified Information Systems Security Professional Official Study Guide. Mike Chapple

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СКАЧАТЬ of physical controls include guards, fences, motion detectors, locked doors, sealed windows, lights, cable protection, laptop locks, badges, swipe cards, guard dogs, video cameras, access control vestibules, and alarms.

      Applicable Types of Controls

      The term security control refers to a broad range of controls that perform such tasks as ensuring that only authorized users can log on and preventing unauthorized users from gaining access to resources. Controls mitigate a wide variety of information security risks.

      Whenever possible, you want to prevent any type of security problem or incident. Of course, this isn't always possible, and unwanted events occur. When they do, you want to detect the events as soon as possible. And once you detect an event, you want to correct it.

      As you read the control descriptions, notice that some are listed as examples of more than one access control type. For example, a fence (or perimeter-defining device) placed around a building can be a preventive control (physically barring someone from gaining access to a building compound) and/or a deterrent control (discouraging someone from trying to gain access).

      Preventive

      A preventive control (aka preventative control) is deployed to thwart or stop unwanted or unauthorized activity from occurring. Examples of preventive controls include fences, locks, authentication, access control vestibules, alarm systems, separation of duties, job rotation, data loss prevention (DLP), penetration testing, access control methods, encryption, auditing, security policies, security-awareness training, antimalware software, firewalls, and intrusion prevention systems (IPSs).

       Keep in mind that there are no perfect security mechanisms or controls. They all have issues that can allow a threat agent to still cause harm. Controls may have vulnerabilities, can be turned off, may be avoided, can be overloaded, may be bypassed, can be tricked by impersonation, may have backdoors, can be misconfigured, or have other issues. Thus, this known imperfection of individual security controls is addressed by using a defense-in-depth strategy.

      Deterrent

      A deterrent control is deployed to discourage security policy violations. Deterrent and preventive controls are similar, but deterrent controls often depend on individuals being convinced not to take an unwanted action. Some examples include policies, security-awareness training, locks, fences, security badges, guards, access control vestibules, and security cameras.

      Detective

A detective control is deployed to discover or detect unwanted or unauthorized activity. Detective controls operate after the fact and can discover the activity only after it has occurred. Examples of detective controls include security guards, motion detectors, recording and reviewing of events captured by security cameras or CCTV, job rotation, mandatory vacations, audit trails, honeypots or honeynets, intrusion detection systems (IDSs), violation reports, supervision and review of users, and incident investigations.

      Compensating

      A compensation control is deployed to provide various options to other existing controls to aid in enforcement and support of security policies. They can be any controls used in addition to, or in place of, another control. They can be a means to improve the effectiveness of a primary control or as the alternate or failover option in the event of a primary control failure. For example, if a preventive control fails to stop the deletion of a file, a backup can be a compensation control, allowing for restoration of that file. Here's another example: if a building's fire prevention and suppression systems fail and the building is damaged by fire so that it is not inhabitable, a compensation control would be having a disaster recovery plan (DRP) with an alternate processing site available to support work operations.

      Corrective

      A corrective control modifies the environment to return systems to normal after an unwanted or unauthorized activity has occurred. It attempts to correct any problems resulting from a security incident. Corrective controls can be simple, such as terminating malicious activity or rebooting a system. They also include antimalware solutions that can remove or quarantine a virus, backup and restore plans to ensure that lost data can be restored, and intrusion prevention systems (IPSs) that can modify the environment to stop an attack in progress. The control is deployed to repair or restore resources, functions, and capabilities after a violation of security policies. Examples include installing a spring on a door so that it will close and relock, and using file integrity–checking tools, such as sigverif from Windows, which will replace corrupted boot files upon each boot event to protect the stability and security of the booted OS.

      Recovery

      Recovery controls are an extension of corrective controls but have more advanced or complex abilities. A recovery control attempts to repair or restore resources, functions, and capabilities after a security policy violation. Recovery controls typically address more significant damaging events compared to corrective controls, especially when security violations may have occurred. Examples of recovery controls include backups and restores, fault-tolerant drive systems, system imaging, server clustering, antimalware software, and database or virtual machine shadowing. In relation to business continuity and disaster recovery, recovery controls can include hot, warm, and cold sites; alternate processing facilities; service bureaus; reciprocal agreements; cloud providers; rolling mobile operating centers; and multisite solutions.

      Directive

A directive control is deployed to direct, confine, or control the actions of subjects to force or encourage compliance with security policies. Examples of directive controls include security policy requirements or criteria, posted notifications, guidance from a security guard, escape route exit signs, monitoring, supervision, and procedures.

      Security Control Assessment

      A security control assessment (SCA) is the formal evaluation of a security infrastructure's individual mechanisms against a baseline or reliability expectation. The SCA can be performed in addition to or independently of a full security evaluation, such as a penetration test or vulnerability assessment.

      The goals of an SCA are to ensure the effectiveness of the security mechanisms, evaluate the quality and thoroughness of the risk management processes of the organization, and produce a report of the relative strengths and weaknesses of the deployed security infrastructure. The results of an SCA may confirm that a security mechanism has sustained its previous level of verified effectiveness or that action must be taken to address a deficient security control. In addition to verifying the reliability of security controls, an assessment should consider whether security controls affect privacy. Some controls may improve privacy protection, whereas others may in fact cause a breach of privacy. The privacy aspect of a security control should be evaluated in light of regulations, contractual obligations, and the organization's privacy policy/promise.

      Generally, an SCA is a process implemented by federal agencies based on NIST SP 800-53 Rev. 5, titled “Security and Privacy Controls for Information Systems and Organizations” (csrc.nist.gov/publications/detail/sp/800-53/rev-5/final). However, though defined as a government process, the concept of evaluating the reliability and effectiveness of security СКАЧАТЬ