Emergency Directive 19-01

January 22, 2019

Mitigate DNS Infrastructure Tampering

This page contains a web-friendly version of the Cybersecurity and Infrastructure Security Agency’s Emergency Directive 19-01, “Mitigate DNS Infrastructure Tampering”. Additionally, see the Director’s blog post.

Section 3553(h) of title 44, U.S. Code, authorizes the Secretary of Homeland Security, in response to a known or reasonably suspected information security threat, vulnerability, or incident that represents a substantial threat to the information security of an agency, to “issue an emergency directive to the head of an agency to take any lawful action with respect to the operation of the information system, including such systems used or operated by another entity on behalf of an agency, that collects, processes, stores, transmits, disseminates, or otherwise maintains agency information, for the purpose of protecting the information system from, or mitigating, an information security threat.” 44 U.S.C. § 3553(h)(1)–(2)

Section 2205(3) of the Homeland Security Act of 2002, as amended, delegates this authority to the Director of the Cybersecurity and Infrastructure Security Agency. 6 U.S.C. § 655(3).

Federal agencies are required to comply with these directives. 44 U.S.C. § 3554 (a)(1)(B)(v)

These directives do not apply to statutorily-defined “national security systems” nor to systems operated by the Department of Defense or the Intelligence Community. 44 U.S.C. § 3553(d), (e)(2), (e)(3), (h)(1)(B).

Background

In coordination with government and industry partners, the Department of Homeland Security (DHS) Cybersecurity and Infrastructure Security Agency (CISA) is tracking a series of incidents1 involving Domain Name System (DNS) infrastructure tampering. CISA is aware of multiple executive branch agency domains that were impacted by the tampering campaign and has notified the agencies that maintain them.

Using the following techniques, attackers have redirected and intercepted web and mail traffic, and could do so for other networked services.

  1. The attacker begins by compromising user credentials, or obtaining them through alternate means, of an account that can make changes to DNS records.
  2. Next, the attacker alters DNS records, like Address (A), Mail Exchanger (MX), or Name Server (NS) records, replacing the legitimate address of a service with an address the attacker controls. This enables them to direct user traffic to their own infrastructure for manipulation or inspection before passing it on to the legitimate service, should they choose. This creates a risk that persists beyond the period of traffic redirection.
  3. Because the attacker can set DNS record values, they can also obtain valid encryption certificates for an organization’s domain names. This allows the redirected traffic to be decrypted, exposing any user-submitted data. Since the certificate is valid for the domain, end users receive no error warnings.

To address the significant and imminent risks to agency information and information systems presented by this activity, this emergency directive requires the following near-term actions to mitigate risks from undiscovered tampering, enable agencies to prevent illegitimate DNS activity for their domains, and detect unauthorized certificates.

Required Actions

Action One: Audit DNS Records

CISA recommends agencies prioritize NS records and those associated with key agency services offered to organizational users and the public (for example, websites that are central to the agency’s mission, MX records, or other services with high utilization).

Action Two: Change DNS Account Passwords

CISA recommends the use of password managers to facilitate complex and unique passwords.

Action Three: Add Multi-Factor Authentication to DNS Accounts

CISA recommends using additional factors that are resilient to phishing. Consistent with NIST SP 800-63b, Short Message Service (SMS)-based MFA is not recommended.

Action Four: Monitor Certificate Transparency Logs

CISA Actions

Reporting Procedures

Agencies shall provide information to CISA per the schedule below:

Beginning February 6, 2019, the CISA Director will engage Chief Information Officers (CIO) and/or Senior Agency Officials for Risk Management (SAORM) of agencies that have not completed required actions, as appropriate, to ensure their most critical federal information systems are adequately protected. By February 8, 2019, CISA will provide a report to the Secretary of Homeland Security and the Director of the Office of Management and Budget (OMB) identifying agency status and outstanding issues.

Duration

This Emergency Directive remains in effect until replaced by a subsequent Binding Operational Directive or terminated through other appropriate action.


Frequently Asked Questions

How far back should I audit my DNS records?

Performing historical analysis of past record changes may be prudent, but it is not part of the directive. Agencies should verify that DNS resource records are currently set to resolve to the intended location, prioritizing as instructed.

In other words, the direction to audit DNS records is an action to stop any current hijacking from occurring, not a requirement to check available DNS or system logs in an effort to evaluate whether a hijack has ever occurred.

My DNS hosting provider doesn’t offer MFA. What should I do?

CISA recommends that you use a provider that offers MFA.

Actions that cannot be completed within the directive’s timetable should be included in your agency’s completion report.

I have non-.gov domains registered, and my registrar does not offer MFA. What should I do?

CISA recommends that you move the domain to a registrar that offers MFA.

Actions that cannot be completed within the directive’s timetable should be included in your agency’s completion report.

You should also be aware that M-17-06 requires executive branch agencies to use a .gov or .mil address for their public-facing digital services, though “the requirement… does not apply in circumstances where the agency is a user or a customer of a third-party website or service that resides on a non-governmental domain”.

Why does the directive exclude the .gov registrar from the requirements around DNS accounts?

User accounts at the .gov registrar are already required to use strong passwords and 2-step verification. They were excluded not because they don’t apply, but because they are already complete.

Before the directive, my agency enforced MFA on accounts that could change DNS records. Do I still need to update passwords on those accounts?

No.

I have console access to a system that can make DNS changes. Do I need to update the system password and add MFA?

No action is required as long as local access to a system is protected by other controls (e.g., physical).

What kind of multi-factor authentication should I be using?

The directive recommends using phishing-resistant authenticators, which includes PIV or the use of security keys.

The use of a combination of two single-factor authenticators is better than accessing a system with just one, and will be accepted under the directive.

What is the role of cloud service providers for this directive?

As there is no managed DNS service offered by the .gov TLD, individual agencies are responsible for managing their own naming services. They might operate it themselves (locally or atop an infrastructure-as-a-service provider) or use a hosted DNS service.

The directive’s scope is agency-managed DNS infrastructure. Where an agency is a user or customer of a third-party website or service, the directive applies solely to agency-managed names that point to that service, not to the service itself.

For example, many agencies use software-as-a-service offerings for mail, web, or collaboration tools. To help users navigate to the service, agencies point a .gov hostname (service.agency.gov) to their service provider (service.provider.com). The action to audit DNS records involves an agency verifying the agency-managed hostname resolves to the proper location. It does not cover the service provider’s domain name and infrastructure.

Agencies might choose to ask their service providers how they ensure their DNS infrastructure is operated securely, and whether change control is protected by multi-factor authentication. This isn’t required under the directive, however, and might not be shared by service providers.

How do I monitor Certificate Transparency logs?

Data from Certificate Transparency logs can alert you that a certificate was issued for a domain you manage. To take full advantage of CT log monitoring, agencies must 1) have a comprehensive inventory of domains they manage (.gov domains are regularly published; your agency may have non-.gov domains registered), and 2) awareness that a certificate request was actually authorized by your organization.

In large organizations with multiple operating divisions, the process of obtaining a certificate may not be centrally managed, and a single entity may not be aware that a given certificate was requested. This gives two possible approaches:

  1. An agency can require that all certificate requests be approved by a central authority, and they can monitor CT log data for unauthorized certificates.
  2. The teams that operate services monitor CT log data themselves for the domains and hostnames they manage.

We strongly recommend the second approach. Where there’s only a single, central feed of CT log data, your organization will need to develop a method to share data for the relevant domains with those teams that can verify a request was authorized. To the greatest degree possible, automate this process.

What do I need in order to monitor Certificate Transparency logs?

In addition to a comprehensive list of all second-level domains your organization manages (.gov and any non-.gov), you’ll need to select a monitoring source.

Footnotes
  1. https://www.us-cert.gov/ncas/current-activity/2019/01/10/DNS-Infrastructure-Hijacking-Campaign 

  2. This includes accounts on agency-managed DNS server software, systems that manage that software, third-party DNS operators’ administration panels, and DNS registrar accounts (excluding the .gov registrar). 

  3. Ibid.