RFY sysAs you can see in the screenshot above, I tried users:sys admin administrator nullbyte root The runescape gold server verified that "sys" and "root" have email accounts on the server. Great!Step 4: Use Smtp User EnumAs you could see in Step 3, we can manually query the SMTP server to see whether a particular email address exists. Wouldn't it be easier if we had a script that did this automatically? Fortunately, we do! It's called smtp user enum and it's built into Kali.
it will still recognize this command and reply appropriately. STARTTLS Normally, SMTP servers communicate in plaintext. To improve security, the connection between SMTP servers can be encrypted by TLS (Transport Layer Security). This command starts the TLS session. RCPT Specifies the email address of the recipient. DATA Starts the transfer of the message contents.
RSET Used to abort the current email transaction. MAIL Specifies the email address of the sender. QUIT Closes the connection. HELP Asks for the help screen. AUTH Used to authenticate the client to the server. VRFY Asks the server to verify is the email user's mailbox exists.
Step 1: Fire Up Kali Open a TerminalNow that we covered the basics of SMTP, let's see if we can use this knowledge to hack the SMTP server to extract email addresses. Let's fire up Kali and open a terminal.Step 2: Telnet into the SMTP ServerOur next step is to see whether we can manually connect to the SMTP server using telnet.
kali > telnet 192.168.1.101 25As you can see, we have successfully connected to the Metasploitable server via telnet.Step 3: Manually Try Email AddressesNow that we are connected via telnet to the SMTP server, we can use the SMTP commands listed above to query the server. Most importantly, we want to use the VRFY (verify) command. Using this command, followed by the email user name, will prompt the server to verify whether the user account exits, such as:
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