Ports – Networking Challenge Writeup | BDSec CTF 2025

1. First open the flag with wireshark.
2. Then write tcp.flags.syn==1 && tcp.flags.ack==1 && ip.addr==192.168.1.5 and press enter.
3. As a result, 6 packets are appeared. Here, count only unique ports.

Why tcp.flags.syn==1 && tcp.flags.ack==1 && ip.addr==192.168.1.5 ? tcp.flags.syn==1 — TCP SYN flag is set (for initiating a TCP connection). tcp.flags.ack==1 — TCP ACK flag is set (acknowledegement)। ip.addr==192.168.1.5 —This filter includes the address as source or destination.