Social networks are designed to facilitate sharing of personal information, and the more data a person discloses, the more valuable he or she is to the service. Unfortunately, these sites have poor track records for security controls. They don't encourage users to select strong passwords, and passwords on these sites never expire. This wouldn't be a problem if people only used these passwords for their social lives, but it's a safe bet that many reuse the same weak passwords--or versions of them--for all of their accounts, including at work.
A database breach last year at RockYou, which creates apps and games for social networking sites, illustrates just how weak passwords can be. Attackers used a SQL injection vulnerability to steal 32 million passwords that were stored in clear text and then posted them to the Internet. This large data set gave us unprecedented insight into the passwords that users select and allowed security researchers to calculate the most common ones (see box on next page).
Attackers often simply try the top 20 passwords when attempting to break into a social network account. Yes, it's a simple dictionary brute-force attack, but if you have a large user base, it's likely at least one of your employees' accounts could be hacked using this method.
Attacker Modus Operandi
Attackers have a variety of ways to guess passwords, including:
>> Brute force based on publicly disclosed information. Beyond the RockYou top 20, people often use names of family members, birthdays, and other personal but easily accessible information in their passwords. Attackers may take what they know about a potential victim and feed it into a program that generates a range of possible passwords.
>> Guessing answers to password-reset questions. Social network users sometimes reveal information that could be used to reset their passwords on the social network itself, Web mail services such as Yahoo Mail, and even on online banking or software-as-a-service sites. For example, some Facebook users include "25 Random Things About You" notes in their profiles. These notes contain information--like mother's maiden name, place of birth, color of a first car--that attackers can use to reset a victim's password and get control of that person's e-mail account.
>> Create a word list to narrow down keywords mentioned in the profile. Several tools can collect keywords from a Web page and put them into a word list (see Easy-To-Find Brute-Force Tools). Once an attacker has this list, he can attempt to brute force the user's password. This attack's effectiveness is largely dependent on how accurate a word list is and whether the social network employs any brute-force prevention mechanisms, such as Captchas, those challenge-response tests used on Web forms to ensure the respondent is a person, not a computer.