What is this strange process `qemu` connecting to minergate.com? I noticed this in Little Snitch:

qemu-system-x86_64
/usr/local/Cellar/qemu/3.0.0/bin/qemu-system-x86_64
Total: 444 B sent, 0 B received
    Outgoing to xmr.pool.minergate.com (78.46.23.253, 46.4.119.208), Port 45700, Protocol TCP (6), 222 B sent, 0 B received
    Outgoing to xmr.pool.minergate.com (78.46.23.253, 46.4.119.208), Port 45700, Protocol TCP (6), 222 B sent, 0 B received


I blocked it but couldn't stop it from reloading. I couldn't find it in LaunchControl. (I never installed qemu via Homebrew.)

Is this some kind of bitcoin mining malware? Any way to figure out where it came from?

For now I just deleted the binary.
Qemu is a virtual emulator. Minergate is mining software. As mentioned it is probably installed via something you installed by Homebrew.

I would recommend a AntiVirus