How to detect negative SEO tactics (spammy backlinks)?

I work for a company who's website has been around since the mid-1990s and it has great information and great domain authority and backlinks. But over the past 10 months we've had an unexplainable drop in search ranking/traffic. I happened to notice in an hrefs report that we've had a HUGE spike in spammy backlinks. The timing of the spammy backlinks uptick roughly lines up with the downward trend in traffic.

Does anyone know how to tell if this it is a negative SEO tactic by a competitor? I know theoretically Google says not to worry about these and they know how to detect them and filter them out but it just seems so coincidental.