Tags: portknocking pcap forensics 

Rating: 1.0

tl;dr:
1. Notice chat and gif about knocking
2. Notice strange port numbers in ascii range
3. Combine port numbers to recover the flag

Full writeup: https://github.com/p4-team/ctf/tree/master/2019-09-07-trendmicro-quals/forensics_100

Original writeup (https://github.com/p4-team/ctf/tree/master/2019-09-07-trendmicro-quals/forensics_100).