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110,995 - Pentesting POP

Reading time: 4 minutes

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Basic Information

Post Office Protocol (POP) is described as a protocol within the realm of computer networking and the Internet, which is utilized for the extraction and retrieval of email from a remote mail server, making it accessible on the local device. Positioned within the application layer of the OSI model, this protocol enables users to fetch and receive email. The operation of POP clients typically involves establishing a connection to the mail server, downloading all messages, storing these messages locally on the client system, and subsequently removing them from the server. Although there are three iterations of this protocol, POP3 stands out as the most prevalently employed version.

Default ports: 110, 995(ssl)

PORT    STATE SERVICE
110/tcp open  pop3

Enumeration

bash
nc -nv <IP> 110
openssl s_client -connect <IP>:995 -crlf -quiet

Manual

You can use the command CAPA to obtain the capabilities of the POP3 server.

Automated

bash
nmap --script "pop3-capabilities or pop3-ntlm-info" -sV -port <PORT> <IP> #All are default scripts

The pop3-ntlm-info plugin will return some "sensitive" data (Windows versions).

POP3 bruteforce

POP syntax

POP commands examples from here

bash
POP commands:
  USER uid           Log in as "uid"
  PASS password      Substitue "password" for your actual password
  STAT               List number of messages, total mailbox size
  LIST               List messages and sizes
  RETR n             Show message n
  DELE n             Mark message n for deletion
  RSET               Undo any changes
  QUIT               Logout (expunges messages if no RSET)
  TOP msg n          Show first n lines of message number msg
  CAPA               Get capabilities

Example:

root@kali:~# telnet $ip 110
 +OK beta POP3 server (JAMES POP3 Server 2.3.2) ready
 USER billydean
 +OK
 PASS password
 +OK Welcome billydean

 list

 +OK 2 1807
 1 786
 2 1021

 retr 1

 +OK Message follows
 From: jamesbrown@motown.com
 Dear Billy Dean,

 Here is your login for remote desktop ... try not to forget it this time!
 username: billydean
 password: PA$$W0RD!Z

Logging Passwords

POP servers with the setting auth_debug enabled will be increasing the logs generated. However, if auth_debug_passwords or auth_verbose_passwords are set as true, password could be also logged in clear text in those logs.

HackTricks Automatic Commands

Protocol_Name:  POP   #Protocol Abbreviation if there is one.
Port_Number:  110     #Comma separated if there is more than one.
Protocol_Description: Post Office Protocol         #Protocol Abbreviation Spelled out

Entry_1:
  Name: Notes
  Description: Notes for POP
  Note: |
    Post Office Protocol (POP) is described as a protocol within the realm of computer networking and the Internet, which is utilized for the extraction and retrieval of email from a remote mail server**, making it accessible on the local device. Positioned within the application layer of the OSI model, this protocol enables users to fetch and receive email. The operation of POP clients typically involves establishing a connection to the mail server, downloading all messages, storing these messages locally on the client system, and subsequently removing them from the server. Although there are three iterations of this protocol, POP3 stands out as the most prevalently employed version.

    https://book.hacktricks.wiki/en/network-services-pentesting/pentesting-pop.html

Entry_2:
  Name: Banner Grab
  Description: Banner Grab 110
  Command: nc -nv {IP} 110

Entry_3:
  Name: Banner Grab 995
  Description: Grab Banner Secure
  Command: openssl s_client -connect {IP}:995 -crlf -quiet

Entry_4:
  Name: Nmap
  Description: Scan for POP info
  Command: nmap --script "pop3-capabilities or pop3-ntlm-info" -sV -p 110 {IP}

Entry_5:
  Name: Hydra Brute Force
  Description: Need User
  Command: hydra -l {Username} -P {Big_Passwordlist} -f {IP} pop3 -V

Entry_6:
  Name: consolesless mfs enumeration
  Description: POP3 enumeration without the need to run msfconsole
  Note: sourced from https://github.com/carlospolop/legion
  Command: msfconsole -q -x 'use auxiliary/scanner/pop3/pop3_version; set RHOSTS {IP}; set RPORT 110; run; exit'

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