In a nutshell, no. Refer to my prior cites for detailed explanations. For a list of real-world attack incidents, see
https://en.m.wikipedia.org/wiki/NTP_server_misuse_and_abuse#<https://en.m.wikipedia.org/wiki/NTP_server_misuse_and_abuse#:~:text=NTP%20server%20misuse%20and%20abuse%20covers%20a%20number%20of%20practices,the%20NTP%20rules%20of%20engagement.> -mel On Aug 6, 2023, at 12:03 PM, Royce Williams <ro...@techsolvency.com> wrote: Naively, instead of abstaining ;) ... isn't robust diversity of NTP peering a reasonable mitigation for this, as designed? Royce On Sun, Aug 6, 2023 at 10:21 AM Mel Beckman <m...@beckman.org<mailto:m...@beckman.org>> wrote: William, Due to flaws in the NTP protocol, a simple UDP filter is not enough. These flaws make it trivial to spoof NTP packets, and many firewalls have no specific protection against this. in one attack the malefactor simply fires a continuous stream of NTP packets with invalid time at your firewall. When your NTP client queries the spoofed server, the malicious packet is the one you likely receive. That’s just one attack vector. There are several others, and all have complex remediation. Why should people bother being exposed to the risk at all? Simply avoid Internet-routed NTP. there are many solutions, as I’ve already described. Having suffered through such attacks more than once, I can say from personal experience that you don’t want to risk it.
