Credential stuffing is the best match because the scenario highlights automated login attempts across many accounts with an unusually high success rate, occurring in the aftermath of a breach. In CEH-aligned system hacking concepts, credential stuffing is the automated testing of known username and password pairs—typically harvested from prior breaches—against a different service. Because many users reuse passwords across sites, attackers often achieve a higher-than-normal success rate compared to guessing-based attacks. This “high success rate” across numerous accounts is a key indicator that the attacker is not randomly guessing, but replaying valid credentials at scale using bots or automation frameworks.

Password spraying differs in that the attacker tries a small set of common passwords (or one password) across many accounts to avoid lockouts. Spraying generally yields a lower success rate and is driven by guessing rather than replaying known credential pairs. A brute force attack is even noisier and typically involves repeated guessing for a single account or small set of accounts; it is both slower and far less likely to produce a high success rate across many users in a short period. Phishing attacks can lead to account takeovers, but the pattern described would more often show targeted victims and varied sources rather than broad, automated, multi-account authentication bursts with consistently successful logins.

CEH defensive guidance emphasizes layered controls: enforce MFA, monitor for abnormal login velocity and credential reuse indicators, deploy bot detection and rate limiting, use breached-password checks, implement adaptive authentication, and tune lockout and detection policies to disrupt automated credential replay without enabling denial-of-service against legitimate users.