Protect Your Domains from Impersonation: Essential Anti-Spoofing Controls
Jul 1, 2024
2 min read
Email spoofing, where attackers impersonate legitimate senders to deceive recipients, poses a significant threat to organisations and their brand reputation. To combat this, email anti-spoofing controls such as SPF, DKIM, and DMARC have become essential controls for businesses aiming to safeguard their domains and preventing impersonation. Let's explore these controls and how they enhance email security.
SPF (Sender Policy Framework)
SPF is a simple email-validation system designed to detect and block email spoofing. It works by allowing domain owners to specify which mail servers are permitted to send emails on behalf of their domain. Here's how SPF enhances email security:
Verification: When an email is received, the receiving server checks the SPF record of the sender's domain to verify if the email was sent from an authorized server.
Prevention: By ensuring emails are sent only from legitimate servers, SPF prevents spammers from sending emails with forged sender addresses.
To implement SPF, domain owners need to add a TXT record to their domain's DNS settings, listing the IP addresses of authorized mail servers.
DKIM (DomainKeys Identified Mail)
DKIM adds a digital signature to outgoing emails, which helps recipients verify that the email hasn't been altered in transit and indeed comes from the claimed sender's domain. Here's how DKIM works:
Signature: When an email is sent, the sender's mail server signs the email with a private key. This signature is added to the email header.
Validation: The recipient's server retrieves the sender's public key from the DNS records to verify the signature. If the signature matches, the email is authenticated.
DKIM not only ensures the integrity of the email but also builds trust by confirming the authenticity of the sender.
DMARC (Domain-based Message Authentication, Reporting & Conformance)
DMARC builds on SPF and DKIM by adding an extra layer of protection and providing a way for domain owners to monitor and mitigate spoofing attempts. Here’s how DMARC enhances email security:
Policy: Domain owners can specify how receiving mail servers should handle emails that fail SPF or DKIM checks (e.g., quarantine or reject).
Reporting: DMARC provides a mechanism for receiving feedback on how emails from the domain are being processed, allowing domain owners to monitor and improve their email security.
To set up DMARC, domain owners create a DNS TXT record that outlines their DMARC policy and reporting preferences.
More Information
The help with implementation of these controls, the NCSC has a useful guide available based on best practice.