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Many online services offer additional security measures. Users can verify their identity with a second factor. This extra protection makes user identification more secure.
Combining a strong password with an authenticator app on a smartphone increases security. The BSI advises using 2FA whenever it is available.
2FA is easy to set up and offers the best protection against account takeovers. Combining a PC and smartphone with secure passwords provides a high level of security.
This section explains why two-factor authentication is important. It lays the groundwork for further, more detailed chapters.
Two Factors: Why an Extra Layer of Protection Matters
Two-factor authentication makes it harder to break in with a stolen password. You need something you know and something you have. This creates independent layers of protection.
Attackers must overcome multiple, technically different elements. This gives users a clear security advantage.
The Basic Principle of Layered Security
The principle uses knowledge, possession, and biometrics. Passwords and PINs fall under knowledge. Smart cards and smartphones fall under possession.
Fingerprints and facial recognition are biometric. Combining these categories creates layered security.
A stolen password is usually not enough. A physical device or biometric characteristic is also needed.
Specific Security Benefits Compared With Password Protection Alone
Data breaches show that passwords are often compromised. 1.3 billion logins were leaked.
Two-factor authentication makes it harder to take over accounts. Using a computer and smartphone for the login and code increases security.
Hardware such as smart cards or FIDO tokens offers even more protection.
BSI Recommendations and the Current Security Landscape
The BSI recommends two-factor authentication wherever possible. Online banking, email, and social networks are especially important.
The BSI says not to disable 2FA. Choose hardware-based solutions or authenticator apps. Layered security is a good protective measure in the current environment.
How Does Logging In With a Second Factor Work?
A login with two factors uses a strong password and an additional safeguard. First, you enter your username and password. Then the system checks whether the information is correct.
The process is simple.
- You enter your login credentials and send them to the server.
- The server checks whether the password is correct.
- Then you must provide a second factor, such as biometrics.
- Access is granted only if both steps are successful.
The system checks the password first and then the second factor. This sequence protects against break-ins.
Some systems check both factors at the same time. For example, with an ID card and PIN. This makes it harder to break into the systems.
It is important for the factors to be different. For example, knowledge (password), possession (smartphone), and biometrics (fingerprint). This keeps you secure.
Codes should be used only for a short time, and devices for the second factor should be kept separate. Hardware keys are also a good idea. You should never rely on just one factor.
| Criterion | Sequential Verification | Integrated Combination |
|---|---|---|
| Verification Sequence | Password first, then the second factor | Linked evaluation of both factors in parallel |
| Security Level | High when the factors are different | Very high through linked authenticity checks |
| Ease of Use | Familiar, easy to understand | Can be more complex, but provides greater transparency about protection |
| Recommended Combination | Password + smartphone OTP or hardware token | ID card + PIN or FIDO token + PIN |
| Vulnerabilities | SIM swaps with SMS codes, phishing | Implementation complexity, higher costs |
Common Authentication Methods: Pros and Cons
We compare different authentication methods. We show their strengths and weaknesses. This helps you make a good decision.
TAN/OTP Systems and Authenticator Apps
TAN and OTP systems generate one-time passwords. These are required after the password. Hardware TAN generators and apps such as Google Authenticator are more secure than paper lists.
eTAN and chipTAN solutions are particularly secure. They link transaction data to the code. Authenticator apps are convenient if you have a backup.
SMS/mTAN: Convenient, but With Risks
SMS codes are widespread and easy to use. However, you should not use the same device to log in and receive codes. This could be dangerous.
Caution is needed when changing SIM cards. You should update your accounts beforehand to ensure delivery remains secure.
Cryptographic Tokens and Hardware Keys (FIDO/U2F)
Cryptographic tokens store private keys. They can be implemented in software or hardware. Hardware offers more protection.
FIDO and U2F standards use physical keys. Services such as WebAuthn support them. The electronic ID card shows how they are used in government systems.
Biometric Methods
Biometrics include fingerprints, facial recognition, and retinal scans. They are convenient and fast. But they are not secret.
Without reliable liveness detection, there is a risk of spoofing. Combining them with a secure key infrastructure is therefore advisable.
Email-based 2FA and other options
Email codes are an option. You should use a separate email address to receive them. This prevents an attacker who has access to your inbox from intercepting codes.
Other options combine multiple methods. They use device-specific certificates. The choice depends on security needs and practicality.
| Method | Advantages | Disadvantages |
|---|---|---|
| TAN/OTP & authenticator apps | Highly practical, time-based codes, offline use possible | Backup required, app theft can increase risk |
| SMS/mTAN | Easy to set up, no additional hardware | Attacks on the SIM or device possible, less secure when using the same device |
| FIDO / U2F token | Very high security, phishing-resistant, hardware-based | Additional device required, administrative overhead for businesses |
| Biometrics | Fast, user-friendly | Not secret, liveness detection required, privacy concerns |
| Email-based 2FA | Convenient, no additional devices | Vulnerable if the email account is compromised |
No method is perfect. FIDO/U2F tokens are ideal for sensitive access. Authenticator apps are good for everyday use. SMS and email are acceptable when additional safeguards are used.
Practical guide: Setting up and managing two-factor authentication
We show you how to set up 2FA and improve your device security. This guide applies to services such as Google, Microsoft, and banks. With a little time and attention, your authentication will become much more secure.
Where and how to enable 2FA
Open your account and go to Settings → Security settings. There, choose your authentication method: app, SMS, token, or biometrics.
With Google, go to “Security” for a simple setup process. Microsoft offers similar menus. Banks provide instructions in online banking, sometimes with videos.
Backup options and recovery
Emergency codes are a good backup option. Store them securely, for example on an encrypted drive.
Keep multiple factors available: a second app, a spare token, or a second number. This helps you avoid lengthy disruptions.
Device security tips
Your smartphone is often the second factor. Use a PIN or biometrics to lock it. Update the operating system and apps regularly.
Disable message previews on the lock screen. Register SIM changes with your carrier. Encrypt backups to protect data.
Important: Do not disable 2FA lightly. Use trusted devices. If you lose a token, activate a replacement and check your services.
Key infrastructure and organizational considerations
Secure two-factor authentication requires more than just user passwords. The technical key infrastructure is important for services to operate reliably. Organizational considerations help establish procedures for device changes and losses.
The role of key stores and certificates
Private keys can be stored in software or hardware. Examples include smart cards and USB tokens. The electronic identity card provides secure storage.
Cryptographic certificates authenticate service providers and users. Hardware storage is more secure than software-based certificates. Online banking uses chipTAN and HBCI, for example.
Integration into business and service provider processes
2FA must be integrated into login and transaction workflows. Businesses should offer interfaces for multiple factors. Emergency procedures are also important.
Technical workflows should allow multiple verification methods. This keeps accounts secure after a device change.
Legal and privacy considerations
Biometric data requires strict protection. Liveness detection and encrypted storage are important. Providers must handle SMS and email in compliance with privacy requirements.
Privacy requirements influence the choice of key storage and certificates. Clear policies and protocols are important.
Practical organizational measures
Before changing SIM cards, users should update their backup codes. Businesses must define procedures for lost devices. Training helps put organizational considerations into practice in everyday activities.
A formal procedure for resets and registering multiple factors improves security. This builds user trust.
Security tips: What to keep in mind and what risks exist
Good security starts with simple rules. Protecting accounts reduces attack surfaces. This improves online security.
Common mistakes and how to avoid them
Many users disable 2FA for convenience. This weakens protection. Another mistake is using 2FA and logging in on the same device.
Device theft or malware renders both factors useless. Recommendation: Keep 2FA enabled and register multiple backup options.
Risks of specific methods and how to mitigate them
SMS/mTAN are popular but carry risks such as SIM swapping and interception. Email codes become less secure when the same email address is used for login and code delivery. Authenticator apps and hardware tokens offer strong protection.
Using two devices, such as a PC and a smartphone, reduces the chance that an attacker controls both. FIDO/U2F security keys offer strong protection against phishing. For transactions, chipTAN or eTAN with transaction binding is recommended.
Recommended combinations for optimal online security
For bank accounts, email, and social networks, the best choice is a strong password plus an authenticator app or a hardware token. For particularly sensitive activities, a combination of possession and knowledge factors plus biometric liveness detection makes sense.
Practical recommended combinations: password + authenticator app for everyday use, password + FIDO security key for high-security accounts, chipTAN/eTAN with transaction binding for payments. These setups minimize risks and provide lasting improvements to online security.
- Short term: Never disable 2FA.
- Medium term: Set up backup factors and save emergency codes.
- Longer term: Use hardware tokens and perform regular checks.
Conclusion
Two factors significantly improve online security. Services with additional authentication protect against account takeovers. Hardware tokens in particular offer strong protection.
A strong password, two devices, and an authenticator or token are ideal. SMS or email are fallback options when no better alternatives are available. Security codes must be stored securely and backed up.
User identification requires consistent action. Do not disable two-factor measures, and update login credentials when switching devices. Two-factor authentication is an important part of online security.
