Binding Operational Directive 18-01

A binding operational directive is a compulsory direction to federal, executive branch, departments and agencies for purposes of safeguarding federal information and information systems. 44 U.S.C. § 3552(b)(1).

The Department of Homeland Security (DHS) develops and oversees the implementation of binding operational directives pursuant to the Federal Information Security Modernization Act of 2014 (“FISMA”). Id. § 3553(b)(2).

Federal agencies are required to comply with these DHS-developed directives. Id. § 3554(a)(1)(B)(ii).

DHS binding operational directives do not apply to statutorily defined “National Security Systems” nor to certain systems operated by the Department of Defense or the Intelligence Community. Id. § 3553(d)-(e).

Enhance Email and Web Security

I. Background

Federal agency “cyber hygiene” greatly impacts user security. By implementing specific security standards that have been widely adopted in industry, federal agencies can ensure the integrity and confidentiality of internet-delivered data, minimize spam, and better protect users who might otherwise fall victim to a phishing email that appears to come from a government-owned system.

Based on current network scan data and a clear potential for harm, this directive requires actions related to two topics: email security and web security.

A. Email Security


When enabled by a receiving mail server, STARTTLS signals to a sending mail server that the capability to encrypt an email in transit is present. While it does not force the use of encryption, enabling STARTTLS makes passive man-in-the-middle attacks more difficult.

Email Authentication

SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) allow a sending domain to effectively “watermark” their emails, making unauthorized emails (e.g., spam, phishing email) easy to detect. When an email is received that doesn’t pass an agency’s posted SPF/DKIM rules, DMARC (Domain-based Message Authentication, Reporting & Conformance) tells a recipient what the domain owner would like done with the message.

Setting a DMARC policy of “reject” provides the strongest protection against spoofed email, ensuring that unauthenticated messages are rejected at the mail server, even before delivery. Additionally, DMARC reports provide a mechanism for an agency to be made aware of the source of an apparent forgery, information that they wouldn’t normally receive otherwise. Multiple recipients can be defined for the receipt of DMARC reports.

B. Web Security

Hypertext Transfer Protocol (HTTP) connections can be easily monitored, modified, and impersonated; HTTPS remedies each vulnerability. HTTP Strict Transport Security (HSTS) ensures that browsers always use an https:// connection, and removes the ability for users to click through certificate-related warnings.

In 2015, OMB M-15-13 required all existing Federal websites and web services to be accessible through a secure connection (HTTPS-only, with HSTS). In 2017, the .gov registry began automatically preloading new federal .gov domains as HSTS-only in modern browsers.

Federal agencies must make more progress on HTTPS and HSTS deployment, including by removing support for known-weak cryptographic protocols and ciphers. According to DHS’s Cyber Hygiene scanning data, seven of the ten most common vulnerabilities seen across federal agency networks at the issuance of this directive would be addressed through complying with the required actions in this directive related to web security.

II. Required Actions

All agencies are required to:

  1. Within 30 calendar days after issuance of this directive, develop and provide to DHS an “Agency Plan of Action for BOD 18-01” to:

    a. Enhance email security by:

    i. Within 90 days after issuance of this directive, configuring:

    • All internet-facing mail servers to offer STARTTLS, and
    • All second-level agency domains to have valid SPF/DMARC records, with at minimum a DMARC policy of “p=none” and at least one address defined as a recipient of aggregate and/or failure reports.

    ii. Within 120 days after issuance of this directive, ensuring:

    • Secure Sockets Layer (SSL)v2 and SSLv3 are disabled on mail servers, and
    • 3DES and RC4 ciphers are disabled on mail servers.

    iii. Within 15 days of the establishment of centralized National Cybersecurity & Communications Integration Center (NCCIC) reporting location, adding the NCCIC as a recipient of DMARC aggregate reports.

    iv. Within one year after issuance of this directive, setting a DMARC policy of “reject” for all second-level domains and mail-sending hosts.

    b. Enhance web security by:

    i. Within 120 days after issuance of this directive, ensuring:

    • All publicly accessible Federal websites and web services provide service through a secure connection (HTTPS-only, with HSTS),
    • SSLv2 and SSLv3 are disabled on web servers, and
    • 3DES and RC4 ciphers are disabled on web servers.
    • Identifying and providing a list to DHS of agency second-level domains that can be HSTS preloaded, for which HTTPS will be enforced for all subdomains.
  2. Upon delivery of its Agency Plan of Action for BOD 18-01 within 30 days of this directive per required action 1, begin implementing that plan.

  3. At 60 calendar days after issuance of this directive, provide a report to DHS on the status of that implementation. Continue to report every 30 calendar days thereafter until implementation of the agency’s BOD 18-01 plan is complete.

III. DHS Actions

IV. Potential Budgetary Implications

DHS understands that compliance with this BOD could result in budgetary implications. Agency Chief Information Officers (CIOs) and procurement officers should coordinate with the agency Chief Financial Officer (CFO), as appropriate.