Multiple Failed Code Attempts - Lockout and Security Response

Quick Answer: The Brute Force Prevention Lockout Mechanism

Smart lock PIN failure lockout implements exponential backoff (3-10 failed attempts triggering 1-15 minute keypad disable) preventing brute force attacks where adversary systematically attempts all possible codes, transforming 4-digit PIN's 10,000 combinations from minutes-to-hours compromise timeline (unlimited attempts) to days-to-weeks timeline (rate-limited attempts) rendering attack impractical. This security mechanism balances legitimate user error tolerance (allowing 3-5 attempts accommodating memory lapses, cold-weather miskeys) against adversary attempt limitation (exponentially increasing lockout durations frustrating systematic enumeration), creating asymmetric defense where legitimate users experience minor inconvenience (2-5 minute waits) while attackers face insurmountable time barriers (24+ hours for complete enumeration).

The lockout threshold variance (3-10 attempts across manufacturers) reflects different security-usability trade-off philosophies: conservative locks (Yale's 3-attempt threshold) prioritize attack prevention accepting higher false-positive lockout rate (legitimate users more frequently locked out), while lenient locks (Kwikset's 10-attempt threshold) prioritize user experience accepting marginally higher attack vulnerability window. This design choice proves consequential: 3-attempt threshold provides 99.97% brute force protection (attacker tries 3, waits 1 min, tries 3 more = 6 attempts in ~2 minutes, requiring ~28 hours for 10,000 combinations), while 10-attempt threshold reduces to 99.9% protection (10 attempts per 5-minute cycle = ~83 hours enumeration time).

Brute Force Attack Time-Complexity Analysis

Before examining lockout strategies, understanding brute force attack mathematics establishes why lockout proves necessary: 4-digit PIN provides 10,000 possible combinations (0000-9999), 6-digit provides 1,000,000, yet without rate limiting adversary attempts all combinations in minutes (assuming 1 second per attempt = 2.8 hours for 4-digit). Lockout mechanisms transform this linear time attack into exponential time attack through forced delays between attempt batches.

Lockout Strategy Security Effectiveness Comparison

Enumeration time calculation example - Yale: Attacker tries 3 codes (9 seconds @ 3 sec/attempt), waits 3 minutes, tries 3 more, waits 5 minutes, tries 3 more, waits 15 minutes... cycling through 10,000 combinations requires 3,333 cycles of "3 attempts + wait", averaging ~8 minutes per cycle (escalating lockouts), totaling ~1,667 hours = 69 days continuous attempt. Practically infeasible.

False positive analysis: Legitimate user entering wrong code 3 times (misremembering PIN) triggers conservative lock 8-12% of users monthly (industry surveys), creating support burden and user frustration, versus lenient lock's 2-4% triggering only for severely confused users or guests receiving incorrect codes.

What Happens During Lockout

Keypad disabled:

☑ No keypad input accepted
☑ Beeps error on button press
☑ May display "Locked Out"
☑ Timer counts down (some models)

Can still:
✓ Unlock via app
✓ Use physical key
✓ Manual thumb turn (interior)

Security Alerts

App notifications:

Alert examples:
- "5 failed PIN attempts at front door"
- "Security alert: Multiple wrong codes"
- "Possible tampering detected"

Includes:
- Time of attempts
- Which attempts  - if codes logged
- Video  - if doorbell integrated

Legitimate Failures

Common Causes

Forgot correct code:

Solution:
□ Use backup access (key, app)
□ Check password manager
□ Ask family member
□ Wait lockout, try again carefully

Misremembered code:

Scenario: Think code is 1234, actually 1243
Result: Multiple failures
Solution:
□ Stop trying
□ Use alternate access
□ Verify code in app
□ Practice correct code

New user confused:

Issue: Guest/family doesn't know process
- Enter code correctly but...
- Didn't press "lock" button after
- Or entered master code instead of theirs

Solution:
□ Clear instructions
□ Walk them through once
□ Write steps if needed

Cold weather issues:

Problem: Fingers numb, can't feel buttons
Result: Pressing wrong keys
Solution:
□ Warm hands first
□ Enter slowly
□ Use backup key
□ Consider biometric (if available)

Threat Model: Distinguishing Legitimate Errors from Adversarial Attempts

Differentiating innocent user error from malicious attack requires behavioral pattern analysis: legitimate failures exhibit random temporal distribution (any time user attempts entry), non-systematic code selection (trying remembered variations, not sequential enumeration), and short attempt bursts (2-5 attempts then stop out of frustration), while adversarial attempts concentrate in low-surveillance windows (late night, when residents away), demonstrate systematic enumeration patterns (sequential codes, common password lists), and persist through multiple lockout cycles (attacker patient, automation-driven).

Attack Vector Classification and Detection

Temporal analysis significance: Failed attempts at 2-4am when residents historically asleep (learned through surveillance or public social media) indicate premeditated attack exploiting minimal detection probability, versus daytime attempts suggesting legitimate access confusion or opportunistic testing. Combined with doorbell motion detection identifying unfamiliar individuals during attempt window, confidence increases to 95%+ malicious classification justifying immediate response.

Immediate Response

If you suspect tampering:

□ Don't ignore
  - Not just "someone made mistake"
  - Could be attempted break-in

□ Check video
  - Doorbell footage
  - Security camera
  - Identify person

□ Review access logs
  - Before failed attempts
  - Any unusual activity?
  - Pattern of attempts?

□ Secure property
  - Change all codes immediately
  - Verify lock not damaged
  - Check doors/windows

□ Consider reporting
  - If clearly malicious
  - Police non-emergency
  - Document for records

Recovery After Lockout

Wait Method

Recommended:

□ Note current time
□ Wait full lockout period
  - Don't try earlier
  - Don't keep testing
  - Be patient

□ After timeout:
  - Try CORRECT code
  - Enter slowly
  - Verify each digit
  - Should work

□ If still locked:
  - Wait another cycle
  - Use backup access
  - Contact support

Alternate Access

Bypass lockout:

□ Use app unlock
  - Keypad locked, app isn't
  - Works normally

□ Use physical key
  - Independent of electronics
  - Always works

□ Manual unlock (inside)
  - Thumb turn
  - If someone home

Prevention

User Education

Prevent legitimate failures:

☑ Clear code documentation
  - Write down for yourself (secure)
  - Don't rely on memory

☑ Practice new codes
  - Before relying on them
  - Test 5 times
  - When not rushed

☑ Guest instructions
  - Step-by-step
  - "Enter 1234 then press lock button"
  - Demonstrate once

☑ Mark button layout
  - If numbers worn off
  - Refresh marking (nail polish)

Security Measures

Prevent attacks:

☑ Don't use obvious codes
  - Not 1234, 0000
  - Not birthday, address
  - Random 6-8 digits

☑ Change codes regularly
  - Every 90 days (high security)
  - After any user leaves

☑ Enable security alerts
  - Failed attempt notifications
  - Review regularly

☑ Add camera
  - Video doorbell
  - See who attempted
  - Deterrent effect

☑ Physical security
  - Good lighting
  - Visible location
  - Neighborhood watch

Brand-Specific Behavior

Yale:

• 5 attempts → 3 min lockout
• Unlimited total attempts
• Alerts via app

Schlage:

• 3 attempts → 1 min
• 3 more → 5 min
• Progressive lockout

Kwikset:

• 10 attempts → 5 min
• More lenient
• May vary by model

August:

• App-based lockout
• PIN attempts logged
• Flexible settings

Factory Reset After Lockout

Permanent lockout (rare):

Some locks after X total failures:
- Keypad permanently disabled
- Requires factory reset
- Check manual for process

Warning:
- Erases all codes
- Lose all settings
- Re-pair required
- Last resort only

Related Resources

Security:

• [Security Best Practices] - /support/secure-smart-lock-best-practices - Prevention
• [Emergency Access] - /support/emergency-battery-died-locked-out - Backup entry

Troubleshooting:

• [Code Not Working] - /support/smart-lock-code-not-working - PIN issues

Summary: Asymmetric Defense Through Exponential Time Complexity

Smart lock PIN lockout mechanisms implement asymmetric cryptographic defense principle (exponential attacker cost, linear defender cost) through rate limiting: legitimate user experiencing lockout waits 2-5 minutes (linear inconvenience), while attacker faces exponential time barriers transforming 2.8-hour brute force attack into 22-83 hour impossibility rendering attack impractical. This mathematical defense proves more robust than complexity-based security alone (6-digit vs 4-digit PIN) since rate limiting affects all PIN lengths equally—increasing digits from 4 to 6 provides 100× more combinations yet still vulnerable to unlimited-attempt enumeration, while 3-minute lockout after 3 attempts provides ~10,000× time multiplier applicable regardless of PIN length.

Threat response prioritization: Distinguish high-probability benign errors (3-5 random attempts during expected entry time, user stops after lockout, matches known household member) from high-probability malicious attempts (10+ sequential codes during late-night window, persistence through multiple lockouts, unfamiliar individual on video) through pattern analysis. Benign incidents require no action beyond user education (remembering correct code, checking app for verification), while malicious incidents demand immediate code rotation, 24-48 hour monitoring escalation, and police reporting documentation establishing attempted burglary.

The lockout paradox: Users frequently perceive lockout as lock malfunction ("it's broken, won't accept any code") rather than recognizing security feature functioning correctly, creating support burden where legitimate lockouts generate customer dissatisfaction despite protecting against adversarial access. Manufacturer documentation must frame lockout as positive security indicator ("your lock prevented unauthorized entry attempt") rather than negative error state, improving user acceptance of inconvenience as necessary security trade-off.