SMTP protocol for sending e-mails
Heuristic analysis
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Anti-relay
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Botnet / Zombie
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Bounce
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Dane
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Denial of service - DDOS
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DKIM
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DMARC
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DNSSEC
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False-negatives
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False positives
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Bayesian filters
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FOVI - President's scam
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FQDN
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Greylisting
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Social Engineering
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White lists
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DNSBl blacklists
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Malware
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MTA / MDA
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Opt-in
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Opt-out
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Ransomware
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Scam / Nigerian419
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Phishing
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SMTP
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Spam
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Spear phishing
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SPF
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StartTLS
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Virus
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Teergrubing
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Turing test
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Definition of SMTP
The SMTP protocol was defined in 1982 by RFC 821. SMTP enables e-mail to be sent over the Internet, and is used to communicate on port TCP/25 between MTA (Mail Transfer Agent) services.
It is one of the oldest Internet protocols, and has always been backward-compatible. The protocol has undergone a few slight changes, with RFC 2821 and the ability to handle attachments via the MIME protocol (RFC 2045 to 2049), but the basis and its primary foundation have remained unchanged. SMTP is a fairly simple protocol, which could almost be reduced to the use of 4 commands: HELO, MAIL FROM, RCPT TO, DATA.
Examples
Example of an SMTP transaction with a mail server:
z03:~# telnet a.mx.mail.yahoo.com 25
220 mta604.mail.mud.yahoo.com ESMTP YSmtp service ready
helo toto.com
250 mta604.mail.mud.yahoo.com
mail from: <toto@toto.com>
250 sender <totot@toto.com> ok
rcpt to: <xxxxxx@yahoo.com>
250 recipient <xxxxxx@yahoo.com> ok
data
354 go ahead
Subject: Test
Test
.
250 ok dirdel
quit
221 mta604.mail.mud.yahoo.com
Application
ALTOSPAM is entirely based on this protocol and analyzes e-mails directly during the SMTP transaction. ALTOSPAM is a service consisting of two SMTP filtering servers.
The online tool provided on the ALTOSPAM website enables you to check DNS servers and SMTP servers for a given domain name.
Email is the main vector for cyberattacks
New and increasingly sophisticated attacks (phishing, spear-phishing, malware, ransomware, viruses, spam) are being launched around the world every day. Our solution detects and neutralizes these threats in real time.
