Brute forcing SMTP passwords

Mail servers often store very sensitive information, and penetration testers need to perform brute force password auditing against them to check for weak passwords.

This recipe will show you how to launch dictionary attacks against SMTP servers by using Nmap.

How to do it...

To launch a dictionary attack against an SMTP server by using Nmap, enter the following command:

$ nmap -p25 --script smtp-brute <target>

If any valid credentials are found, they will be included in the script output section:

25/tcp  open  stmp    syn-ack
| smtp-brute: 
|   Accounts
|     acc0:test - Valid credentials
|     acc1:test - Valid credentials
|     acc3:password - Valid credentials
|     acc4:12345 - Valid credentials
|   Statistics

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