What are “attack surfaces” in email?

Attack surfaces are vulnerabilities attackers can exploit. In email, surfaces include: DNS records (poisoning, hijacking), SMTP infrastructure (compromise, relay abuse), user credentials (phishing, credential stuffing), and content processing (malware, exploits).

Sender-side surfaces: ESP accounts, API keys, sending domains, and authentication configurations. Compromising any enables sending malicious email appearing to come from legitimate sources.

Recipient-side surfaces: inbox access, client vulnerabilities, and user behavior. Attackers target these through phishing, malicious attachments, and social engineering. Minimizing attack surfaces requires securing each potential vulnerability.