Timestamp-seeded keys
Some early scripts generated keys from the clock — sha256(timestamp) or an RNG seeded with the time. That turns 2^256 possibilities into merely "how many seconds are there?"
How it works
If a key is derived from the moment it was created — for example sha256(Date.now()) or a generator seeded with time() — then the only unknown is when the wallet was made. Scan every second from Ethereum's genesis (30 July 2015) to today and you have covered every possibility: only a few hundred million values, checkable in minutes.
This mode scans exactly that: one candidate key per second across the chain's lifetime, hashing the decimal timestamp string the way naive scripts did.
Why it is a real risk
Time is the classic "looks random but isn't" seed. It appears unpredictable to a human but is trivially enumerable for a machine, and an attacker who knows roughly when a wallet was created can narrow the range even further. The catastrophic Milk Sad vulnerability was fundamentally this mistake — a Mersenne Twister seeded with the system time — dressed up behind a respectable-looking mnemonic.
The defense
Never seed key material from the clock, a counter, or any low-entropy source. Use a cryptographically-secure RNG that draws from the operating system's entropy pool (getrandom, /dev/urandom, crypto.getRandomValues).