🐯 Tiger — VNC Warmup Walkthrough

By Hasnain Abid, HackViser Ambassador

In this Upskills warmup challenge, we explore misconfigurations in a Virtual Network Computing (VNC) service. This challenge teaches how insecure remote desktop services can expose entire systems without requiring credentials.

This write-up walks through every task step-by-step, including enumeration, VNC access, process inspection, and log analysis.

🖥️ What is VNC?

VNC (Virtual Network Computing) is a protocol that allows graphical remote control of a machine over the network. It uses the RFB (Remote Framebuffer) protocol to send:

• screen updates
• keyboard input
• mouse events

Because VNC is often misconfigured, it can sometimes be accessed without a password, leading to full desktop compromise.

🔍 Task 1 — What does VNC stand for?

Answer: Virtual Network Computing

🔍 Task 2 — Which port is open?

We begin by scanning the target:

nmap -T5 <target-ip>

From the result:

5901/tcp open vnc

Open port: 5901

🖧 Task 3 — Which user did we establish a VNC session with?

Using Remmina (or any VNC viewer), connect to:

<target-ip>:5901

The connection succeeds without a password, showing insecure VNC configuration.

Inside the remote desktop terminal:

whoami

User: *l***

🐧 Task 4 — Linux Kernel Version

Inside the terminal, run:

uname -r

Output:

5.10.0-28-amd64

Kernel: 5.10.0–28-amd64

🛠️ Task 5 — Name of the Running VNC Program

List active processes:

ps aux | grep vnc

Result shows processes like:

/usr/bin/vncserver
/usr/bin/****ervnc

The running VNC server is:

Program: Xtigervnc

📜 Task 6 — IP Address That Connected on Feb 23, 2023

Navigate into the VNC folder:

cd /home/leo/.vnc
ls -la

You will see a file:

connections.log.backup

View it:

cat connections.log.backup

The log shows:

Thu Feb 23 08:35:42 2023 <IP-address>

Author

Hasnain Abid HackViser Ambassador Cybersecurity Researcher | Penetration Tester | Ethical Hacker