So the service you used this password at gets its password hashes leaked. Your account is one of the (admittedly many) low-hanging fruits that gets used for whatever else someone might be using it for.
I suppose, if it's some random forum, they could just post some bot spam with your account and get you banned, no big deal. You'll live.
Ah! That's a good point. I had been considering a hash leak to be equivalent to a plaintext password leak, where you're screwed no matter the entropy. But I guess you have a fair point: a high entropy password could prevent your password from being cracked even under that scenario. So you could have a point here.
We could explore that further: are there any recent examples of this happening? is cracking password hashes still hard, given modern GPU hardware techniques? This could help us establish what "low" actually means when I say "low threshold."
Yes it still happens pretty regularly, but in recent years people have gotten a lot better at using libs, so passwords are salted and hashed with a slow algorithm which substantially increases the difficulty of hashed attacks by makign it computationally expensive to hash every password. These days it's not uncommon for it to take months or years to crack 50% of the passwords in a dump. If your password has sufficient entropy, it may never be cracked. Modern GPUs can parallelize across their numerous cores, but statistically a brute force isn't going to work. Hybrid dictionary attacks are where it's at, and if your password is random (pseudo-random) then a dict attack won't work.
> is cracking password hashes still hard, given modern GPU hardware techniques
Yes, if the entropy is high enough. What else would be the point of salting and hashing passwords?
There's no known way to reverse major hash algorithms like SHA-256 or bcrypt; you have to try all the combinations. So you have to do exponential work in the amount of entropy whereas GPUs only give a constant factor speedup over CPUs.
If this ever changes (e.g., someone breaks SHA-256 or bcrypt) you will definitely see it as the #1 story on HN (and probably pretty prominently in mainstream media too).
I suppose, if it's some random forum, they could just post some bot spam with your account and get you banned, no big deal. You'll live.