The episode says Roman installed Kameo on exposed Windows computers to scrape payment-card data, although the episode also frames the attribution as presumptive in places.
UncertainConfidence 90% · Jack RhysiderEP 32Details
“he’d install malware on it to scrape the cards off it and then send it to his server”
Kameo infected Windows computers, including the Windows systems used by the affected businesses; the transcript does not specifically say Kameo ran on Windows 8.