This problem gives us a file that runs as an x86 ELF binary as well as a 16-bit bootable disk image in QEMU. The program deobfuscates the code based on password input provided by the user.
The first password QMU displays the phrase EMULATOR.
The second password EMULATOR displays the phrase BOOTING and reveals the phrase OBSCUREDISCOVERY.
The third password BOOTING opens a socket and waits for a connection.
The fourth password OBSCUREDISCOVERY is sent through a connection to the listening socket and the correct flag is returned.

Original writeup (https://speeeday.wordpress.com/2018/06/19/small-uiuctf-2018/).