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“Interim” No More: DHS and DOJ Publish Final CISA Guidance on Cybersecurity Sharing 

The Department of Homeland Security (DHS) and the Department of Justice (DOJ) have issued the long-awaited final procedures for both Federal and Non-Federal Entities under the Cybersecurity Information Sharing Act (CISA) (“Final Procedures”) that provide information on how DHS will implement CISA.  In addition to the Final Procedures, the agencies also released “Guidance to Non-Federal Entities to Share Cyber Threat Indicators and Defensive Measures with Federal Entities under the Cybersecurity Information Sharing Act of 2015 (the “Guidance”).

As we have written previously, a company may share cyber threat indicators (CTIs) and defensive measures (DMs) for cybersecurity purposes “notwithstanding any other provision of law,” and receive certain liability protections for sharing in accordance with the Act.  The Final Procedures and the Guidance are finalized versions of interim guidance previously discussed.  Any decision to share information under CISA is complex and involves factual and legal determinations.

Read on to find out what CTIs and DMs are, and information on the procedures companies must follow to obtain liability protection for sharing CTIs and DMs with the Federal Government.  

What is a Cyber Threat Indicator (CTI)?

The Final Procedures describe a CTI as “information necessary… to describe or identify a cybersecurity threat or vulnerability.”  A CTI can identify how a threat or vulnerability is exploited, for example, “a method of defeating a security control.”  A CTI can also describe what happened, such as the consequences of an exploited threat, for example, “a description of information” that was stolen.

What is a Defensive Measure (DM)?  

A DM “detects, prevents, or mitigates a known or suspected cyber security threat or vulnerability.”  Typically DMs will be provided by a company’s external vendors, or set up by internal IT staff.  An example of a defensive measure would be a firewall rule that prevents malicious traffic, or a program that identifies malicious activity.

What Should a Company Not Include As Part of a Shared CTI or DM?

The “CISA requires a non-federal entity to remove any information from a cyber threat indicator or defensive measure that it knows at the time of sharing to be personal information of a specific individual or information that identifies a specific individual that is not directly related to a cybersecurity threat before sharing that cyber threat indicator or defensive measure with a federal entity.”  Complying with this is a two-step process.

First, before sharing a CTI or DM a company should review and assess whether it contains personal information of a specific individual or identifies a specific individual.  While situations like this should be infrequent, the statute and the guidance dirt that such an assessment be performed prior to sharing and an internal protocol should be developed and implemented to make these assessments.  However, describing the how of a CTI, or what happened, should typically be possible without including personal information or identifying individuals.  Nor should describing a DM that prevents or identifies threats commonly contain this type of information.

Second, if personal information or information that identifies a specific individual is present, the company needs to decide if it is “directly related” to a cybersecurity threat.  For example, the Guidance suggests that if a spear phishing email was circulated and sent to certain persons in a company, personal information contained in the "From" (sender) and "Subject" lines and the content of the message itself might validly be “directly related” to a cybersecurity threat, while the names of targets in the "To" line might now.  Situations of this type should be carefully evaluated as part of the threat-sharing assessment process.

The CISA includes categories of information “unlikely to be directly related to a cybersecurity threat” such as:

  • Protected Health Information (PHI)
  • Human Resources Information
  • Consumer Information/History, such as an individual’s purchases, preferences, or credit.
  • Educational History
  • Financial Information, including loan information and credit reports.

Procedures Companies Must Follow to Obtain Liability Protection for Sharing CTIs and DMs with the Federal Government

One of the important components of CISA is the "safe harbor": private companies can receive liability protection for sharing CTIs and DMs with the Federal Government.  According to the statute:   “[S]uch sharing receives liability protection under section 106(b)(2) when conducted with the federal government through the DHS capability and process, or as otherwise permitted under section 105(c)(1)(B).”

The first step (and critical step in the analysis of whether to share in the first place) is ensuring that a company is only sharing valid CTIs and DMs as described above, as CISA does not afford liability protection for the sharing of information that fails to comport with the requirements of the statute.  

The DOJ/DHS guidance document also contains a footnote stating that:  “While not the focus of this guidance, private entities also receive liability protection under section 106(b)(1) for sharing cyber threat indicators and defensive measures with other private entities in accordance with CISA.”

Second, to ensure the availability of CISA's liability protections when sharing directly with the Federal Government, companies must share any CTIs and DMs through an approved mechanism with the Department of Homeland Security (DHS).  Effective use of these methods will likely require close consultation with appropriate IT staff.  The approved methods are:

  • Automated Information Sharing (AIS) initiative
  • Web Form
  • Email
  • Other information sharing programs that use these means of receiving cyber threat indicators or defensive measures.

The Guidance provides additional detail on each of these sharing mechanisms, summarized briefly below.

AIS Initiative

Automated Information Sharing (AIS) requires the use of specialized software at the company to communicate with DHS in an automated manner.  On the company side, this specialized software is called a Trusted Automated eXchange of Indicator Information (TAXII) client.  This client software communicates the CTIs and DMs to be shared to a server at DHS in a secure and automated manner.    Complete information about AIS, including the Terms of Use, is online, and should be reviewed by legal and operational stakeholders before making a determination whether to participate in CISA.

Web Form

Companies may share CTIs and DMs with DHS’s National Cybersecurity and Communications Integration Center by filling out a web form on a DHS website.


Companies may share CTIs and DMs with DHS’s National Cybersecurity and Communications Integration Center (NCCIC) by sending an email to a designated NCCIC email address that contains certain descriptive parameters.

Other DHS Programs through which Cyber Threat Indicators and Defensive Measures May Be Shared Using the DHS Capability and Process

Companies can also share CTIs and DMs by using programs that leverage automated machine-to-machine sharing, web forms or email.  For example, DHS provides access to communities of interest (such as industrial control systems owners and operators) through a web-based portal, which allows sharing of indicators via web form or secure messaging capabilities within the portal.  However, should a company decide to pursue a custom solution that leverages an approved method, such as machine-to-machine sharing, care should be taken to ensure that it does indeed comport with an approved DHS method.

What Now?

Companies must thoroughly evaluate the costs, benefits and risks associated with participating in the information sharing process. If your cyber security system or threat defenses are considered a competitive advantage, you may decide to limit sharing to a particular circumstance or a particular threat or incident.  Further, companies should consult with experienced legal counsel regarding the litigation risks posed by both sharing and receiving threat information.  In either case, your company should be prepared to mitigate the incident that it has reported, or assess and respond to the threat information it receives.  Failure to do so exposes the company to later claims by plaintiffs that the company failed to adequately address known risks, particularly in the aftermath of a data breach.

A company that decides to share information under CISA should make certain that it has procedures and systems in place to collect, screen, and report the information it plans to share—particularly because CISA’s protections apply only when sharing is conducted in accordance with the law’s specific requirements. Additional considerations exist for public companies, as information sharing under CISA may implicate securities laws insofar as sharing cyber information could be considered material information requiring disclosure in a public filing.

We will be diving deeper into all of these issues over the coming months as CISA is implemented and companies begin assessing the value and the risks of participating in sharing and receiving specific cyber threat information.

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Cynthia J. Larose

Member / Co-Chair, Privacy & Cybersecurity Practice

Cynthia J. Larose is Chair of the firm's Privacy & Cybersecurity Practice, a Certified Information Privacy Professional-US (CIPP-US), and a Certified Information Privacy Professional-Europe (CIPP-E). She works with clients in various industries to develop comprehensive information security programs on the front end, and provides timely counsel when it becomes necessary to respond to a data breach.