SI-3 SI · System and Information Integrity

Malicious Code Protection

✓ LOW ✓ MODERATE ✓ HIGH
4 Enhancements 1 Overlay 19 Related Controls
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Requirements NIST SOURCE

    1. 1.Perform periodic scans of the system [frequency] and real-time scans of files from external sources at [one of: endpoint; network entry and exit points] as the files are downloaded, opened, or executed in accordance with organizational policy; and
    2. 2.[one of: block malicious code; quarantine malicious code; take] ; and send alert to [personnel or roles] in response to malicious code detection; and
Discussion (NIST Supplemental Guidance)

System entry and exit points include firewalls, remote access servers, workstations, electronic mail servers, web servers, proxy servers, notebook computers, and mobile devices. Malicious code includes viruses, worms, Trojan horses, and spyware. Malicious code can also be encoded in various formats contained within compressed or hidden files or hidden in files using techniques such as steganography. Malicious code can be inserted into systems in a variety of ways, including by electronic mail, the world-wide web, and portable storage devices. Malicious code insertions occur through the exploitation of system vulnerabilities. A variety of technologies and methods exist to limit or eliminate the effects of malicious code. Malicious code protection mechanisms include both signature- and nonsignature-based technologies. Nonsignature-based detection mechanisms include artificial intelligence techniques that use heuristics to detect, analyze, and describe the characteristics or behavior of malicious code and to provide controls against such code for which signatures do not yet exist or for which existing signatures may not be effective. Malicious code for which active signatures do not yet exist or may be ineffective includes polymorphic malicious code (i.e., code that changes signatures when it replicates). Nonsignature-based mechanisms also include reputation-based technologies. In addition to the above technologies, pervasive configuration management, comprehensive software integrity controls, and anti-exploitation software may be effective in preventing the execution of unauthorized code. Malicious code may be present in commercial off-the-shelf software as well as custom-built software and could include logic bombs, backdoors, and other types of attacks that could affect organizational mission and business functions. In situations where malicious code cannot be detected by detection methods or technologies, organizations rely on other types of controls, including secure coding practices, configuration management and control, trusted procurement processes, and monitoring practices to ensure that software does not perform functions other than the functions intended. Organizations may determine that, in response to the detection of malicious code, different actions may be warranted. For example, organizations can define actions in response to malicious code detection during periodic scans, the detection of malicious downloads, or the detection of maliciousness when attempting to open or execute files.

Enhancements NIST SOURCE

SI-3(1) Central Management WITHDRAWN

Withdrawn. Incorporated into PL-9.

SI-3(2) Automatic Updates WITHDRAWN

Withdrawn. Incorporated into SI-3.

SI-3(3) Non-privileged Users WITHDRAWN

Withdrawn. Incorporated into AC-6(10).

SI-3(4) Updates Only by Privileged Users LOW MODERATE HIGH

Update malicious code protection mechanisms only when directed by a privileged user.

Discussion

Protection mechanisms for malicious code are typically categorized as security-related software and, as such, are only updated by organizational personnel with appropriate access privileges.

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SI-3(5) Portable Storage Devices WITHDRAWN

Withdrawn. Incorporated into MP-7.

SI-3(6) Testing and Verification LOW MODERATE HIGH
  1. (a) Test malicious code protection mechanisms [frequency] by introducing known benign code into the system; and
  2. (b) Verify that the detection of the code and the associated incident reporting occur.
Discussion

None.

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SI-3(7) Nonsignature-based Detection WITHDRAWN

Withdrawn. Incorporated into SI-3.

SI-3(8) Detect Unauthorized Commands LOW MODERATE HIGH
  1. (a) Detect the following unauthorized operating system commands through the kernel application programming interface on [system hardware components]: [unauthorized operating system commands] ; and
  2. (b) [one of: issue a warning; audit the command execution; prevent the execution of the command].
Discussion

Detecting unauthorized commands can be applied to critical interfaces other than kernel-based interfaces, including interfaces with virtual machines and privileged applications. Unauthorized operating system commands include commands for kernel functions from system processes that are not trusted to initiate such commands as well as commands for kernel functions that are suspicious even though commands of that type are reasonable for processes to initiate. Organizations can define the malicious commands to be detected by a combination of command types, command classes, or specific instances of commands. Organizations can also define hardware components by component type, component, component location in the network, or a combination thereof. Organizations may select different actions for different types, classes, or instances of malicious commands.

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SI-3(9) Authenticate Remote Commands WITHDRAWN

Withdrawn from the catalog.

SI-3(10) Malicious Code Analysis LOW MODERATE HIGH
  1. (a) Employ the following tools and techniques to analyze the characteristics and behavior of malicious code: [tools and techniques] ; and
  2. (b) Incorporate the results from malicious code analysis into organizational incident response and flaw remediation processes.
Discussion

The use of malicious code analysis tools provides organizations with a more in-depth understanding of adversary tradecraft (i.e., tactics, techniques, and procedures) and the functionality and purpose of specific instances of malicious code. Understanding the characteristics of malicious code facilitates effective organizational responses to current and future threats. Organizations can conduct malicious code analyses by employing reverse engineering techniques or by monitoring the behavior of executing code.

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Implementation Guidance

Engineering Interpretation

Original engineering commentary written for this explorer — not NIST source text and not authoritative guidance.

No engineering interpretation has been authored for SI-3 yet. This section is architected to receive it — see the Requirements and Assessment sections above for the authoritative NIST source content in the meantime.

Assessment

NIST SP 800-53A REV 5.2.0

Assessment Objectives

  1. one or more of the following PARAMETER VALUES is/are selected: {signature-based; non-signature-based};
  2. the frequency at which malicious code protection mechanisms perform scans is defined;
  3. one or more of the following PARAMETER VALUES is/are selected: {endpoint; network entry and exit points};
  4. one or more of the following PARAMETER VALUES is/are selected: {block malicious code; quarantine malicious code; take <SI-03_ODP[05] action>};
  5. action to be taken in response to malicious code detection are defined (if selected);
  6. personnel or roles to be alerted when malicious code is detected is/are defined;
  7. <SI-03_ODP[01] SELECTED PARAMETER VALUES> malicious code protection mechanisms are implemented at system entry and exit points to detect malicious code;
  8. <SI-03_ODP[01] SELECTED PARAMETER VALUES> malicious code protection mechanisms are implemented at system entry and exit points to eradicate malicious code;
  9. malicious code protection mechanisms are updated automatically as new releases are available in accordance with organizational configuration management policy and procedures;
  10. malicious code protection mechanisms are configured to perform periodic scans of the system <SI-03_ODP[02] frequency>;
  11. malicious code protection mechanisms are configured to perform real-time scans of files from external sources at <SI-03_ODP[03] SELECTED PARAMETER VALUES> as the files are downloaded, opened, or executed in accordance with organizational policy;
  12. malicious code protection mechanisms are configured to <SI-03_ODP[04] SELECTED PARAMETER VALUES> in response to malicious code detection;
  13. malicious code protection mechanisms are configured to send alerts to <SI-03_ODP[06] personnel or roles> in response to malicious code detection;
  14. the receipt of false positives during malicious code detection and eradication and the resulting potential impact on the availability of the system are addressed.

Examine

[SELECT FROM: System and information integrity policy; system and information integrity procedures; configuration management policy and procedures; procedures addressing malicious code protection; malicious code protection mechanisms; records of malicious code protection updates; system design documentation; system configuration settings and associated documentation; scan results from malicious code protection mechanisms; record of actions initiated by malicious code protection mechanisms in response to malicious code detection; system audit records; system security plan; other relevant documents or records].

Interview

[SELECT FROM: System/network administrators; organizational personnel with information security responsibilities; organizational personnel installing, configuring, and/or maintaining the system; organizational personnel responsible for malicious code protection; organizational personnel with configuration management responsibilities].

Test

[SELECT FROM: Organizational processes for employing, updating, and configuring malicious code protection mechanisms; organizational processes for addressing false positives and resulting potential impacts; mechanisms supporting and/or implementing, employing, updating, and configuring malicious code protection mechanisms; mechanisms supporting and/or implementing malicious code scanning and subsequent actions].

Overlays

OT/ICS Overlay SP 800-82r3

NIST SP 800-82r3 Appendix F, Table 22. Blank baseline means the control/control enhancement is not selected in that initial OT baseline.

LOW

  • Base control: Included (matches standard baseline)

MODERATE

  • Base control: Included (matches standard baseline)

HIGH

  • Base control: Included (matches standard baseline)

STIGs & CCIs

No STIG checks or CCI mappings are currently loaded for SI-3. This section is architected to display, per product: STIG ID, Finding ID, Severity, Title, Description, Check, Fix, CCI, and NIST control mapping — but nothing is populated here until a real DISA STIG/CCI dataset is ingested.

Learn more about STIG/CCI integration →

Evidence

Potential Evidence — Derived

Categorized from the SP 800-53A "Examine"/"Test" artifact list above by keyword — not an authoritative NIST evidence list.

Policy

  • System and information integrity policy
  • system security plan

Configuration

  • configuration management policy and procedures
  • system design documentation
  • system configuration settings and associated documentation

Testing

  • Organizational processes for employing, updating, and configuring malicious code protection mechanisms
  • organizational processes for addressing false positives and resulting potential impacts
  • mechanisms supporting and/or implementing, employing, updating, and configuring malicious code protection mechanisms
  • mechanisms supporting and/or implementing malicious code scanning and subsequent actions

Other Records

  • system and information integrity procedures
  • procedures addressing malicious code protection
  • malicious code protection mechanisms
  • records of malicious code protection updates
  • scan results from malicious code protection mechanisms
  • record of actions initiated by malicious code protection mechanisms in response to malicious code detection
  • system audit records
  • other relevant documents or records