Stats
Actions
Tags
From cybersecurity-skills
Audits and deploys SPF, DKIM, and DMARC records to prevent domain spoofing and email phishing. Includes DNS checks, key generation, and policy configuration.
How this skill is triggered — by the user, by Claude, or both
Slash command
/cybersecurity-skills:implementing-dmarc-dkim-spf-email-securityThe summary Claude sees in its skill listing — used to decide when to auto-load this skill
SPF, DKIM, and DMARC form the three pillars of email authentication. Together they prevent domain spoofing, validate message integrity, and define policies for handling unauthenticated mail. Proper implementation drastically reduces phishing attacks that impersonate your organization's domain.
SPF, DKIM, and DMARC form the three pillars of email authentication. Together they prevent domain spoofing, validate message integrity, and define policies for handling unauthenticated mail. Proper implementation drastically reduces phishing attacks that impersonate your organization's domain.
Publishes a DNS TXT record listing authorized IP addresses and mail servers that can send email on behalf of your domain. Receiving servers check the envelope sender's IP against this list.
Adds a cryptographic signature to outgoing emails using a private key. The corresponding public key is published in DNS. Receivers verify the signature to ensure the message was not altered in transit.
Builds on SPF and DKIM by specifying a policy (none/quarantine/reject) for messages that fail authentication, and provides a reporting mechanism to monitor spoofing attempts.
# Check existing SPF record
dig TXT example.com | grep spf
# Check existing DKIM selector
dig TXT selector1._domainkey.example.com
# Check existing DMARC record
dig TXT _dmarc.example.com
# DNS TXT record for example.com
v=spf1 ip4:203.0.113.0/24 include:_spf.google.com include:spf.protection.outlook.com -all
Key SPF mechanisms:
ip4: / ip6: - Authorize specific IP rangesinclude: - Include another domain's SPF recorda - Authorize domain's A record IPsmx - Authorize domain's MX record IPs-all - Hard fail all others (recommended)~all - Soft fail (monitoring phase)# Generate DKIM key pair (2048-bit RSA)
openssl genrsa -out dkim_private.pem 2048
openssl rsa -in dkim_private.pem -pubout -out dkim_public.pem
# Format public key for DNS (remove headers, join lines)
grep -v "PUBLIC KEY" dkim_public.pem | tr -d '\n'
DNS TXT record at selector1._domainkey.example.com:
v=DKIM1; k=rsa; p=MIIBIjANBgkqhki...
# DNS TXT record at _dmarc.example.com
# Phase 1 (Monitor):
v=DMARC1; p=none; rua=mailto:[email protected]; ruf=mailto:[email protected]; pct=100
# Phase 2 (Quarantine):
v=DMARC1; p=quarantine; rua=mailto:[email protected]; pct=25
# Phase 3 (Reject):
v=DMARC1; p=reject; rua=mailto:[email protected]; pct=100
Use the scripts/process.py to parse DMARC aggregate XML reports and identify authentication failures, unauthorized senders, and spoofing attempts.
npx claudepluginhub costrict-plugins-repo/mukul975-anthropic-cybersecurity-skills-cybersecurity-skillsImplements SPF, DKIM, and DMARC email authentication to prevent domain spoofing and phishing. Covers DNS record setup, key generation, and policy configuration.
Implements SPF, DKIM, and DMARC email authentication via DNS records, key generation, and audits to prevent spoofing and phishing attacks.
Guides implementing SPF, DKIM, and DMARC email authentication protocols to prevent spoofing and phishing. Covers DNS TXT records, OpenSSL key generation, dig audits, and server configs.