Booted up my new MacBook Air and got the message 10 times with the exact same string of random numbers and letters afterward, at exactly 8:06 AM PDT today. I was looking at a college website. Nothing is slowed down, and I did a scan and everything turns out peachy keen. Nothing is running slower, and there have been no more warnings since. I’m hoping it’s a false positive, that a streaming update (as someone mentioned) may have been the cause of it. But, as a precaution I have e-mailed avast.