Perimeter
1/21/2009
02:53 PM
Robert Graham
Robert Graham
Commentary
Connect Directly
RSS
E-Mail
50%
50%

How Hackers Will Crack Your Password

I've been cracking passwords lately for pen tests, and I'm surprised at how corporate guidelines don't really help people choose passwords. As in many places in security, a disconnect exists between how people secure systems and how hackers break systems. So the following is a brief description of what hackers do (or, at least, what I do when pen-testing systems).

I've been cracking passwords lately for pen tests, and I'm surprised at how corporate guidelines don't really help people choose passwords. As in many places in security, a disconnect exists between how people secure systems and how hackers break systems. So the following is a brief description of what hackers do (or, at least, what I do when pen-testing systems).The first problem is an "online" vs. "offline" attack. An online attack is where hackers try to log on pretending to be you and guess your password. Unless you've chosen something extremely easy to guess (such as "Wasila High"), this isn't a big danger. Online systems automatically lock your account after too many bad guesses.

The real danger is "offline" cracking. Hackers break into a system to steal the encrypted password file or eavesdrop on an encrypted exchange across the Internet. They are then free to decrypt the passwords without anybody stopping them.

Doing this, hackers can guess passwords at the rate of 1 billion guesses a second. That's fast, but not when you consider how big the problem is. Consider passwords composed of letters, numbers, and symbols. That's roughly 100 combinations per character. A five-character password will have 10 billion combinations. This means a hacker can guess a five-character password in only 10 seconds. But things quickly get worse for the hacker. This problem grows exponentially:

    5 characters = 10 seconds 6 characters = 1,000 seconds 7 characters = 1 day 8 characters = 115 days 9 characters = 31 years 10 characters = 3,000 years

This is why you need long passwords. Hackers can usually crack anything with seven characters or fewer, but they would be unlikely to guess passwords using this technique that are nine characters or more.

This is also why you need complex passwords containing uppercase and lowercase, numbers, and symbols. That's 100 possible combinations for each character. Lowercase passwords have only 26 combinations per character. A hacker can guess an all-lowercase password of 10 characters in about two days.

However, hackers have another trick up their collective sleeve: the mutated dictionary attack. Because of the above problem, you might choose a large password, like "Aardvark-Zebra9." This is longer than what a hacker will be able to discover by brute force. So hackers solve this with a "dictionary" attack. Instead of trying all combinations of characters, they instead try to match passwords with words in a dictionary. They then "mutate" the words, reflecting common things people do to passwords.

When users are told to make their passwords complex, they usually do something simple to them. Instead of choosing "robert" as a password, they will make it "robert!". Putting an exclamation mark at the end of a password is one of the most common mutations people choose. Hackers know this, so their dictionary cracks will do the same thing.

Here is a list of common mutations a hacker will try to dictionary words:

  • capitalizing the first letter of a word;
  • checking all combinations of upper/lowercase for words;
  • inserting a number randomly in the word;
  • putting numbers on the ends of words;
  • putting numbers on the beginning of words;
  • putting the same pattern at both ends, like *foobar*;
  • replacing letters like "o" and "l" with numbers like "0" and "1";
  • punctuating the end of words;
  • duplicating the first letter, or all letters in the word;
  • combining two words together; and
  • putting punctuation or space between the words.

Hackers are also smart about which words they choose. They don't just choose English words, but also include most popular languages (i.e., Spanish, French, German). They also choose words from pop culture, like xbox360 or Britney Spears.

If they know who you are, they will find words particular to you. Let's say your name is "John Smith," you drive a "BMW," you work for "Microsoft," and you like to watch "The Office." A hacker will Google these terms and create wordlists from the resulting Web pages. Thus, "Carell325i" seems like a fine 10-character password to defeat hackers, but will get cracked in only a few minutes by a hacker who knows you. (I like to use the Associative Word List Generator Web site to generate password lists for me.)

So how do you choose something that hackers can't guess? Well, remember that hackers aren't all-powerful. Increased complexity of things they have to check, the less likely they will guess your password. Yes, they will check for numbers on the ends of passwords, but as long as you've chosen something like your birthdate instead of 1234, it's something more likely to be missed.

Including just one international character, like a vowel with an umlaut, will defeat most password crackers. They can be typed by holding down the key and typing a -three-digit number on the numpad. Typing long phrases instead of words will also help. In theory, it should be easy to guess "Twas as a dark and stormy night" as a passphrase, but in practice, hackers won't catch it. On the flip side, the more complex you make your password, the harder it will be for you to type it in. Try to create something as long as you can comfortably type, while still keeping in mind the techniques above.

Robert Graham is CEO of Errata Security. Special to Dark Reading

Comment  | 
Print  | 
More Insights
Comments
Newest First  |  Oldest First  |  Threaded View
anon7008839568
50%
50%
anon7008839568,
User Rank: Apprentice
4/14/2014 | 11:16:15 PM
Correction
"They can be typed by holding down the key" should be "They can be typed by holding down the ALT key"
Register for Dark Reading Newsletters
Partner Perspectives
What's This?
In a digital world inundated with advanced security threats, Intel Security seeks to transform how we live and work to keep our information secure. Through hardware and software development, Intel Security delivers robust solutions that integrate security into every layer of every digital device. In combining the security expertise of McAfee with the innovation, performance, and trust of Intel, this vision becomes a reality.

As we rely on technology to enhance our everyday and business life, we must too consider the security of the intellectual property and confidential data that is housed on these devices. As we increase the number of devices we use, we increase the number of gateways and opportunity for security threats. Intel Security takes the “security connected” approach to ensure that every device is secure, and that all security solutions are seamlessly integrated.
Featured Writers
White Papers
Cartoon
Current Issue
Dark Reading's October Tech Digest
Fast data analysis can stymie attacks and strengthen enterprise security. Does your team have the data smarts?
Flash Poll
Title Partner’s Role in Perimeter Security
Title Partner’s Role in Perimeter Security
Considering how prevalent third-party attacks are, we need to ask hard questions about how partners and suppliers are safeguarding systems and data.
Video
Slideshows
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2014-3409
Published: 2014-10-25
The Ethernet Connectivity Fault Management (CFM) handling feature in Cisco IOS 12.2(33)SRE9a and earlier and IOS XE 3.13S and earlier allows remote attackers to cause a denial of service (device reload) via malformed CFM packets, aka Bug ID CSCuq93406.

CVE-2014-4620
Published: 2014-10-25
The EMC NetWorker Module for MEDITECH (aka NMMEDI) 3.0 build 87 through 90, when EMC RecoverPoint and Plink are used, stores cleartext RecoverPoint Appliance credentials in nsrmedisv.raw log files, which allows local users to obtain sensitive information by reading these files.

CVE-2014-4623
Published: 2014-10-25
EMC Avamar 6.0.x, 6.1.x, and 7.0.x in Avamar Data Store (ADS) GEN4(S) and Avamar Virtual Edition (AVE), when Password Hardening before 2.0.0.4 is enabled, uses UNIX DES crypt for password hashing, which makes it easier for context-dependent attackers to obtain cleartext passwords via a brute-force a...

CVE-2014-4624
Published: 2014-10-25
EMC Avamar Data Store (ADS) and Avamar Virtual Edition (AVE) 6.x and 7.0.x through 7.0.2-43 do not require authentication for Java API calls, which allows remote attackers to discover grid MCUser and GSAN passwords via a crafted call.

CVE-2014-6151
Published: 2014-10-25
CRLF injection vulnerability in IBM Tivoli Integrated Portal (TIP) 2.2.x allows remote authenticated users to inject arbitrary HTTP headers and conduct HTTP response splitting attacks via unspecified vectors.

Best of the Web
Dark Reading Radio
Archived Dark Reading Radio
Follow Dark Reading editors into the field as they talk with noted experts from the security world.