Is this mold in the attic

I really don't have time to write a good answer, but I have and others have written some good responses that would answer your question. Look at the tags for mold. ID is important before remediation can be done. You have to know what kind of mold you are dealing with. Some minor mold can be dealt with DIY, but other toxic molds need professional attention. Samples need to be taken and IDed by a lab. Don't take chances, get it right.

What's the humidity level in the room? I'd go get a $12 humidity sensor and see what you got. My understanding that mold can grow >= 60% RH, though there are other factors (e.g. moisture will condense on a cold wall with a lower relative humidity). You may need a dehumidifier if you're too high. Of course that won't kill the mold but will keep it from growing.