What Is Password Spray Attack and How to Prevent It

What Is Password Spray Attack and How to Prevent It

VPN provider Citrix, whose clientele includes more than 400,000 organizations including 98% of the Fortune 500 companies, recently disclosed that cybercriminals gained access and downloaded business documents from its internal network.

According to the Federal Bureau of Investigation (FBI), the one that informed Citrixabout the illegal intrusion, the attackers likely used a tactic known as password spray to gain a foothold with limited access to Citrix’ network and worked to circumvent additional layers of security.

What Is Password Spray Attack?

Password spray is a type of cyberattack that attempts to access a large number of usernames (accounts) using commonly used passwords. This type of attack is also known as low-and-slow method as an attacker or attackers at first attempt to login using a single commonly used password for a number of usernames. If the first password is incorrect for all the usernames, the attackers will then use a different password, giving sufficient time in between different password guessing so as not to trigger any time-based account lockout thresholds.

Attackers, for instance, can easily get all usernames of a certain organization using the toolMailsniperand then attempt to login using at first the commonly used password “[email protected]$$w0rd” on all of the usernames, and if this password fails, after a sufficient time interval, use another commonly used password “Password1” and so on.

Password spray is a stealth form of cyberattack, evading most detection techniques. On the part of the legitimate user or the organization, login attempts that are part of password spray attacks are seen as isolated failed login.

On the part of the attackers, password spray attack is a numbers game. Even though commonly used passwords are used only by 0.5-1.0% of accounts, one successful attempt for every thousand accounts attacked is enough as this one successful attempt has a multiplying effect. Successful access to one account allows attackers to harvest further information.

A study conducted by the UK National Cyber Security Center (NCSC)showed that 75% of the participants’ organizations (UK-based) had accounts with passwords that featured in the top 1,000 passwords, and 87% had accounts with passwords that featured in the top 10,000.

"This data suggests that password spraying attacks are likely to have some success against these organizations, and many other organizations across the UK,” NCSC said. “Whilst account lockout policies may limit attackers to trying (for example) 10 passwords against a single account per day, the account lockout counters usually reset over time. This allows persistent attackers to try more passwords, and they can (and do) end up trying hundreds or even thousands of common passwords.”

Prevalence

The recent cyberattack on Citrix via password spray attack shows that cybercriminals are increasingly using this form of cyberattack against organizations worldwide. In March 2018, the U.S. Department of Homeland Security (DHS) and the FBI released a joint alertwarning the public against the growing threat of password spray attacks.

Passwords aren’t just used in emails. They’re also used in single sign-on (SSO) or web-based applications with federated authentication method. According to DHS and FBI, victims of password spray attacks often use SSO or web-based applications with federated authentication method. DHS and FBI added that the vast majority of known password spray victims share some of the following characteristics:

• Lack of multifactor authentication (MFA)
• Allow easy-to-guess passwords (“[email protected]$$w0rd” or “Password1”)
• Use inbox synchronization, allowing email to be pulled from cloud environments to remote devices
• Allow email forwarding to be setup at the user level

In March 2018, theFBIannounced the hacking-related charges against nine Iranians. The FBI said the accused conducted a 4-year campaign that compromised nearly 144 U.S.-based universities and 176 foreign universities in 21 countries. In addition to the compromised universities, the FBI said 50 U.S. and foreign private companies, the states of Hawaii and Indiana and the United Nations were compromised by the accused as well.

Over 30 terabytes of academic data and intellectual property, equivalent to 3 times the amount of data contained in the print collection of the Library of Congress, were stolen by the accused, the FBI said.

According to the FBI, the accused compromised their victims through password spray attacks. “They were flying under the radar,” said the FBI agent who investigated the case, “and the magnitude of their effort was remarkable.”

How to Prevent Password Spray Attacks

While password spray attacks can go undetected by security networks, there are, however, indicators of this type of cyberattack. Indicators of password spray attacks include the rise in attempted logins against the enterprise SSO portal or web-based application, and employee logins from IP addresses resolving to locations not consistent with their normal locations.

Here are some measures aimed at deterring password spray attacks:

1. Use Multifactor Authentication (MFA)

Using MFA in all active, internet facing protocols is one way to deter password spray attacks. So long as there are passwords, attackers would forever guess them. MFA is a means to distinguish between a legitimate account owner and the attacker.

2. Ban Commonly Used Passwords

Banning commonly used passwords is another means to deter password spray attacks. Every password creation, change or reset should run through a banned password checker, containing a list of words that no one should ever have in their password.

3. Use Non-Password-Based Access Methods

Password spray attacks exist because of passwords. When passwords aren’t used at all, there would be no passwords that the attackers have to guess. Instead of passwords, use non-password-based authentication methods.

For instance, Windows Server 2016 enables completely password-free access based on strong cryptographic keys tied to both the user and the device.