They're running a brute force preimage attack against all bitcoin addresses which currently have a balance. The reason they say "collision" is that if they foun

They're running a brute force preimage attack against all bitcoin addresses which currently have a balance. The reason they say "collision" is that if they found a key that hadn't been made weak on purpose, it would probably be a different key from the original (bitcoin addresses do not map 1-to-1 with keys).