Steam
Steam
Steam has faced DDoS attacks a couple of times, though I haven't heard it fully compromised. Players usually are responsible, as games are tied to accounts. When you purchase a game, you receive an email receipt proving ownership. If any part is missing, reach out to Steam support and wait a few months for resolution.
Steam's security measures are quite strong, and it seems they haven't been completely compromised. Usually, issues arise when people share their login details publicly.