No. of Recommendations: 2
From the thread responses, I would guess the following separate issues:

-- The malicious requests from your IP may be coming from elsewhere and that your IP address was spoofed. Nothing on your system. Or it may be an exploit on your ISP's machines.
-- The fact that your password and keychain access went back to normal after a reboot implies to me that something resident in memory (RAM) was corrupted but not something on disk. That sort of thing happens to me every once in a while if I haven't shutdown or restarted in a very long time.

It's good that you checked with Malwarebytes, but unless this happens with increasing frequency going forward, I wouldn't be very concerned other than to keep an eye out for recurrence.

Speculation: On some Ubuntu systems I run, I've noticed what appears to be a bug in some server software that accumulates external IP addresses from unsuccessful logins. The IP addresses accumulate, and when additional unsuccessful logins are attempted, all those IP addresses result in multiple DNS lookups from my machine(s). A reboot usually clears out those addresses, but it winds up looking like the machines are used for DDOS attacks in a botnet. Fortunately or unfortunately, I don't have any proof that my machines are being exploited deliberately as part of a botnet. It really looks like a bug, and it may have been resolved in Ubuntu 17 -- not sure yet. (All that crap that Linux users used to claim about open software being readily fixed by developers is just that -- crap. Issues in Linux, if reported at all, pile up forever, and developers with other, real-world jobs fix them on their own sweet time, if ever.)

I don't know if macOS has the same problem -- I doubt it -- but if there's a similar problem with the OS, it may be resulting in making your machine look like part of a malicious botnet, hence the possibility that your machine may be the one sending the malicious requests. But my first guess is your machine isn't the problem.

-awlabrador
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