Open the packet capture with Wireshark. There seems to be some HTTP traffic in this file -- let's try to export HTTP objects!

Seems like there's a very suspicious file from *www.evil.isitdtu.com*. Exporting it gives the following!

flag=O4ZWY3C7MQYG4M27NAZXEM27GFZV66JQOVZF6ZTMGRTQ%3D%3D%3D%3D

Putting this into an online cipher identifier identifies this as a base 32 encoded string. Therefore, simply use a base 32 decoder to get the flag:

isitdtu{w3ll_d0n3_h3r3_1s_y0ur_fl4g}