These lists are rarely from a single new breach. Instead, they are typically Compilations of Multiple Breaches (COMB) , where hackers aggregate data from thousands of past leaks into one searchable database.
The "207k" likely refers to the number of entries (approximately 207,000) within the file, while "USA" suggests the credentials belong to users based in the United States. 207k usa combo.txt
Malicious actors use these lists to fuel credential stuffing attacks. Since many people reuse passwords across different sites, an attacker can take this list and use automated tools to try those same credentials on high-value sites like banks, retailers, or social media. Why These Files Circulate Combo Breach - Aura Help Center These lists are rarely from a single new breach