Stay secure with the latest email security updates, best practices, and threat alerts to protect your inbox and sensitive information.
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Background for this topic.
Email is a system for exchanging digital messages, typically using mail servers and clients over a network. In security, it includes both the messages and the accounts, servers, domains, and authentication mechanisms that handle them. Email commonly carries phishing links, malicious attachments, and fraudulent requests for payments or credentials; compromised accounts can also be used to impersonate trusted people and conduct further attacks.
Defenses include filtering and malware scanning, phishing-resistant multifactor authentication, careful handling of links and attachments, and monitoring for unusual login or sending activity. Domain controls such as SPF, DKIM, and DMARC help receiving systems detect messages that are forged or sent without authorization, while encryption protects message contents in transit or at rest when correctly implemented. Security teams should preserve relevant headers and mailbox activity so suspicious messages can be investigated, removed, and used to identify affected accounts and other recipients.
Three newly discovered SMTP smuggling attack techniques can exploit misconfigurations and design decisions made by at least 50 email-hosting providers.
The tactic is not new, but there has been a steady increase in its use as of this spring.