I'm aware there are now articles about this, and that it's somewhat old news now, at the time of writing and for a number of hours afterwards the only two in google were the one I linked and one from I think it was the sun that had no more information. This was sent Saturday at 11am Eastern and just got stuck in moderation for a while (which isn't a dig at the moderators, especially as it was a weekend, just a note that the situation in terms of information when it was sent and when most people got this had changed significantly). I'm also aware of the discussion on the outages list, in fact I was the one who started that discussion at about the same time I sent this (I think it was a few minutes after this email that I sent the one to outages). On 2021-11-13 11:02, Glenn McGurrin via NANOG wrote:
I had a bit of an odd one this morning, I received two emails through contacts listed in whois subject: "Urgent: Threat actor in systems" from "eims@ic.fbi.gov". I was all set to ignore them as an odd bit of spam but did a quick check on the headers and was surprised to see it had valid dkim and spf and was from an actual FBI IP, queue real worry starting. Luckily it looks like it was a case of something being hacked on the FBI's end as calling they immediately knew what I was calling about and said they had dealt with the compromised equipment. Further googling after that call shows a few more reports of this ex. https://twitter.com/spamhaus/status/1459450061696417792 and https://www.newsweek.com/fbi-email-system-reportedly-hacked-fake-dhs-cyberat... but I'd figured to mention it here so others don't get caught quite as off guard.
Best guess I can come up with is it's an attempt to ruin the person mentioned in the email's name and/or promote the name of the mentioned gang. The specifics seem off for trying to get someone swatted given if you thought this was real what local agency would want to storm a federal operation with swat agents, and if you thought this was all fake, then you wouldn't go either. That or create FUD for any other warnings issued and distract from something else going on.
Full body of the email:
Our intelligence monitoring indicates exfiltration of several of your virtualized clusters in a sophisticated chain attack. We tried to blackhole the transit nodes used by this advanced persistent threat actor, however there is a huge chance he will modify his attack with fastflux technologies, which he proxies trough multiple global accelerators. We identified the threat actor to be Vinny Troia, whom is believed to be affiliated with the extortion gang TheDarkOverlord, We highly recommend you to check your systems and IDS monitoring. Beware this threat actor is currently working under inspection of the NCCIC, as we are dependent on some of his intelligence research we can not interfere physically within 4 hours, which could be enough time to cause severe damage to your infrastructure. Stay safe, U.S. Department of Homeland Security | Cyber Threat Detection and Analysis | Network Analysis Group