Simple Mail Transfer Protocol (SMTP): 25

Security Weaknesses

• Open relay configuration can allow unauthorized email forwarding.

• Susceptible to email spoofing and phishing.

• Plaintext transmission of messages and credentials if not secured.

Security Defense and Mitigation Measures

• Configure SMTP with STARTTLS or SMTPS for encryption.

• Use SPF, DKIM, and DMARC to authenticate and verify emails.

• Monitor outgoing emails for unusual patterns or volumes.

Indicators of Compromise or Attack

• Large volumes of outbound emails indicating spam activity.

• Emails flagged as spoofed or phishing by recipients.

• Increased bounce-back messages due to invalid recipients.