A YubiKey is a hardware security key used to prove identity during login or privileged actions. It typically works with phishing-resistant authentication methods such as FIDO2/WebAuthn, and in some setups it can also support OTP or smart-card style functions. Because the secret is stored in the device and the user must physically touch or insert it, a YubiKey adds a strong second factor that is much harder to steal remotely than a password or SMS code.
In cyber security, YubiKeys are used to protect email, cloud accounts, developer tools, and administrator access. Defenders rely on them to reduce account takeover, while attackers may target the human workflow around them through theft, social engineering, or proxy phishing that tries to capture a valid login session. Customization projects can change how a token looks and feels, which is harmless in itself but can affect how carefully people handle or identify the device. Security hardware works best when its purpose stays obvious and distinct.