Enterprises can't just store cryptographic hashes of user passwords and think they are protected, as attackers spend the time and resources to run them against dictionaries.
Cyber-attackers
have access to various tools to launch their campaigns, such as scanning
Websites and applications for vulnerabilities, crafting
malicious emails and launching
drive-by-download Web portals. They have a growing body of information and
automated password cracking tools to breach systems and networks, Imperva said
in a report.
Cyber-attackers
have greater access to rainbow tables and dictionaries to aid them in cracking
passwords, Imperva researchers wrote in their monthly Hacker Intelligence
Initiative report released Dec. 14. Organizations have to beef up their
password security practices to prevent attackers from successfully guessing
passwords and getting access to the network, Imperva said.
Imperva
analyzed a list of nearly 100,000 passwords that were exposed by a data breach
at film enthusiast Website FilmRadar.com. The site had stored user passwords
using the SHA1 hash function, which is a common method used to secure
applications, but it wasn't enough, according to Imperva. The strength of a
cryptographic hash is irrelevant because attackers can bypass the protections
and guess what the password is, Imperva found.
"Contrary
to common belief, cryptographic hash functions in general-whether they are
SHA-1 or any other cryptographic function-are not impervious to hackers,"
Imperva researchers wrote in the report.
Password
cracking tools that make use of rainbow tables and dictionaries are readily
available, and most of them are free for anyone to download, Imperva said. Some
popular cracking tools include MD5 decrypter, Cyberwar Zone, Cain and Able, and
John the Ripper, according to the report. Many of the tools also rely on hacker
forums as a way to request and get additional tables and dictionaries.
"With
enough determination, a hacker can easily find tools and multiple dictionaries
for password cracking," Imperva researchers wrote.
Rainbow
tables contain hash values that have already been precomputed for a large
number of alphanumeric text. Although creating these tables is generally a
lengthy process, once created, they can be reused over and over again. If the
attacker has a hashed value of a password for a specific service, all that
needs to be done is to look up the hash in the table and find the corresponding
alphanumeric string. Imperva found a hacker Website that makes a rainbow table
with more than 50 billion hashed values available to the public.
Strong
passwords-those with multiple character types, such as both lowercase and
uppercase letters, numbers and special characters, as well as long ones-make it
computationally difficult to look up the hash in the rainbow table. However,
researchers have recently shown that harnessing the power of cloud, such as renting
out computing resources from Amazon Elastic Compute Cloud (EC2) can reduce
the time required.
Dictionaries
are similar in that they list common passwords with a precalculated hash value.
Dictionary-based attacks are effective because as people are still using simple
and common passwords, such as "Hello123" and "abcd123."
Imperva
ran some of the publicly available tools against the FilmRadar passwords. The
team managed to uncover 77 of the 100 most popular passwords in less than 10
minutes using rainbow tables hosted on an online service, according to the
report. The 100 most common passwords on the list accounted for 10 percent of
the list. Nearly 5 percent of all passwords were guessed in less than two days
using dictionaries. Even though it was a slow process, hackers could figure out
passwords using multiple dictionaries, Imperva said.
"When
it comes to consumers implementing good passwords, we give up. Instead of
consumers, [the] responsibility rests on enterprises to put in place proper
password security policies and procedures as a part of a comprehensive data
security discipline," Imperva researchers said. IT and security teams
should consider passwords as highly valuable data, even if PCI and other regulations
don't apply, according to Imperva.
Imperva
recommends that enterprises not rely on just cryptographic hashes, but to
"salt" the entries to protect against rainbow table attacks. A salt
value is a random value that is added to the beginning of the password before
it gets encrypted, making it even harder to crack the password. A salt of just
three-bit length increases the storage and precomputation time for rainbow
tables eightfold, according to Imperva.
Enterprises
should use passphrases, longer passwords that are easier to remember.
Passphrases result in long passwords, but users don't need to worry about
writing them down on to a Post-It. Password security should also be enforced,
by comparing the password against the same dictionaries being used by
attackers. Microsoft recently banned common passwords on its Hotmail Webmail
service.
"Advice
to users is to choose strong passwords. The rest is up to the business,"
Imperva said.
The
"Imperva
Enterprise Password Worst Practices" report follows an earlier report
from 2009 on poor consumer password practices.
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