We have extracted a pcap file from a network where attackers were present. We know they were using some kind of file transfer protocol on TCP port 7179. We're not sure what file or files were transferred and we need you to investigate. We do not believe any strong cryptography was employed.

Hint: The file you are looking for is a png
Hint: The key is not in the bytes, its in the png itself.

pcapin_73c7fb6024b5e6eec22f5a7dcf2f5d82.pcap