Understanding Password Security
How Password Strength is Measured
Password strength is a measure of how effective a password is at resisting guessing and brute-force attacks. Several factors contribute to the overall strength assessment:
Entropy
Entropy is the mathematical measure of how unpredictable a password is, typically measured in bits. Each bit of entropy doubles the number of guesses needed to find the password. A strong password should have at least 70-80 bits of entropy.
Character Set Complexity
The variety of characters used in a password significantly affects its strength:
- Lowercase letters (a-z): 26 possible characters
- Uppercase letters (A-Z): 26 additional characters
- Numbers (0-9): 10 additional characters
- Special characters (!@#$%^&*, etc.): 33+ additional characters
Using all four character types increases the possible combinations exponentially, making passwords harder to crack.
Password Length
Length is one of the most critical factors in password strength. Each additional character multiplies the number of possible combinations:
Dictionary Resistance
Dictionary attacks attempt to crack passwords by trying common words and phrases. Strong passwords should not include:
- Common dictionary words
- Common names
- Common phrases or quotes
- Song lyrics or movie quotes
- Simple word-number combinations (password123)
Common Password Attack Methods
Understanding how passwords are attacked helps illuminate why certain password practices are recommended. Here are the most common methods attackers use:
Brute Force Attacks
This approach systematically checks all possible combinations of characters until the correct password is found.
How It Works:
The attacker tries every possible combination of letters, numbers, and symbols, usually starting with shorter combinations and working up to longer ones.
Defense:
Long passwords with high entropy dramatically increase the time required for a successful brute force attack, often making it computationally infeasible.
Dictionary Attacks
This method uses a predefined list of words, phrases, and common passwords to attempt access.
How It Works:
Attackers leverage lists containing millions of words from dictionaries, previously leaked passwords, names, and common phrases.
Defense:
Avoid using common words. If you use a dictionary word, substantially modify it with symbols, numbers, and uncommon capitalization patterns.
Rainbow Table Attacks
This technique uses precomputed tables to crack password hashes more efficiently than brute force methods.
How It Works:
Rainbow tables contain precomputed hashes of possible passwords, allowing attackers to look up password hashes rather than computing them on the fly.
Defense:
Modern password hashing algorithms use "salting" (adding random data to each password before hashing) to defend against rainbow table attacks.
Social Engineering
This non-technical approach manipulates users into revealing their passwords.
How It Works:
Attackers might pose as IT support, send phishing emails, or research personal details to guess passwords based on information about the target.
Defense:
Never share passwords, be suspicious of unsolicited communications asking for credentials, and don't use easily guessable personal information in passwords.
Credential Stuffing
This attack uses previously leaked username/password combinations on multiple services.
How It Works:
After a data breach, attackers attempt to use the same credentials on other websites, exploiting the fact that many people reuse passwords.
Defense:
Use unique passwords for every account and enable two-factor authentication where available.
Password Cracking Speed Evolution
The computational power available for password cracking has increased dramatically over time:
A typical desktop computer could check approximately 10 million passwords per second against unsalted MD5 hashes.
GPU-based cracking reached billions of attempts per second, rendering many previously secure passwords vulnerable.
Specialized hardware could check hundreds of billions of passwords per second against older hash algorithms.
Cloud-based distributed cracking tools and specialized ASIC hardware continue to increase attack capabilities, making passwords under 10 characters increasingly vulnerable.
Password Security Misconceptions
Many common beliefs about password security are outdated or were never accurate to begin with:
Reality: Frequent mandatory password changes often lead to weaker passwords and predictable patterns (e.g., Password1, Password2). Modern guidance from NIST and other security organizations recommends changing passwords only when there's reason to believe they've been compromised.
Reality: These substitutions are so common that modern password crackers automatically try them. "P@ssw0rd" is not significantly more secure than "Password".
Reality: Modern cracking hardware can attempt all possible 8-character combinations, even with full complexity, in a matter of days or weeks. Length is now more critical than complexity.
Reality: Password crackers specifically check for this pattern. Adding "123!" to the end of a word provides minimal additional security.
Reality: Password hints often provide enough information for attackers to guess the password, especially if they can access information about you from social media.
Reality: Many security questions ask for information that is either publicly available or easy to research (mother's maiden name, birthplace, first school). They often create additional vulnerabilities rather than enhancing security.
Building a Password Security Strategy
A comprehensive password security strategy involves several components:
1. Password Manager
A password manager creates and stores strong, unique passwords for each service. You only need to remember one master password. Benefits include:
- Automatic generation of strong, unique passwords
- Secure storage with encryption
- Autofill capability to prevent typing (and potential keylogging)
- Cross-device synchronization
- Breach alerts when your credentials appear in known data breaches
Popular options include Bitwarden (open-source), 1Password, LastPass, and KeePass (offline).
2. Multi-Factor Authentication (MFA)
MFA requires multiple forms of verification, typically:
- Something you know: Your password
- Something you have: Your phone, a hardware key, etc.
- Something you are: Biometric data like fingerprints
Even if your password is compromised, attackers still can't access your account without the second factor. Prioritize enabling MFA on:
- Email accounts (often used for password resets)
- Financial accounts
- Cloud storage services
- Social media accounts
- Work/professional accounts
3. Passphrase Approach
For passwords you must memorize (like your password manager's master password), consider using passphrases - a series of random words. They're easier to remember but hard to crack due to length.
For even greater security, add capitalization, numbers, or symbols: Purple7Monkey!DishwasherSunset
4. Password Hygiene Practices
- Never reuse passwords across accounts
- Don't share passwords, even with trusted contacts
- Avoid entering passwords on public or shared computers
- Check regularly for breaches affecting your accounts
- Log out of sensitive accounts when not in use
- Review active sessions and connected apps periodically
What to Do After a Password Breach
If a service you use announces a data breach, or you suspect your password has been compromised, follow these steps:
Change the affected password immediately
Create a new, strong password for the compromised account.
Check for unauthorized activity
Review account activity, transaction history, sent emails, or other actions that might indicate an attacker accessed your account.
Change similar passwords on other sites
If you've used the same or similar passwords elsewhere, change those too.
Enable two-factor authentication
Add this extra layer of security to prevent future unauthorized access.
Monitor your accounts
Keep a close eye on affected accounts for suspicious activity.
Consider credit monitoring
If financial or highly sensitive accounts were affected, consider credit monitoring services to catch potential identity theft.
Helpful Resources for Breach Response
- Have I Been Pwned - Check if your email has appeared in known data breaches
- IdentityTheft.gov - US government resource for reporting and recovering from identity theft
- Your country's consumer protection agency or data protection authority