What Your Login Success Rate Says About Your Credential Stuffing Threat

One of the problems with imitation attacks such as sophisticated credential stuffing is that they are designed to blend in with legitimate traffic. How can you measure something that you can’t detect? Fear-mongering marketing compounds this problem and makes everything sound like a snake-oil solution for a problem people don’t think they have.

Imitation attacks against your services and APIs leverage inherent functionality in your system. In other words, they can be successful even when you have patched, firewalled, and done everything perfectly from an application security standpoint. Blocking basic credential stuffing attacks generated from naive bots is straightforward but, as attackers evolve, they develop more sophisticated tools to launch attacks that blend in with legitimate traffic better. They use machine learning to emulate user behavior like mouse movements and keystrokes. They generate or harvest digital fingerprints to distribute across a botnet to make each node appear more “real.” They proxy requests through residential IP addresses to give the traffic the appearance of originating from known-good home networks. Googles themselves make tools like Puppeteer & headless Chrome to automate and script the world’s most common browser which is exactly what you would use if you were trying to blend in with legitimate users. This is a problem that is getting harder, not easier.

Imitation attacks like advanced credential stuffing do have one thing in common, though – they send millions of requests hoping that a fraction of a percentage end up successful and result in an account takeover, a valid credit card, an account number with a loyalty balance, anything. This success/failure ratio is observable with data you have now. What we’ve found at Shape, is that similar companies have similar success ratios for similar user experience flows.

If you’re debating if you have a credential stuffing problem, then take a long look at your login success ratio.

What is your average login success ratio?

The average login success ratio drops dramatically during periods of credential stuffing attacks. These attacks use combolists with millions of usernames and passwords and of course the majority of these credentials aren’t valid on your site. Shape sees credential stuffing success rates between .2 and 2%, typically – attackers don’t need a very high success rate as long as the attack is cheap to perform. These attacks push the login success rate for your site down well below normal numbers. Some Shape customers have seen login success ratios lower than 5% before enabling countermeasures. Success ratios that low are abnormal and should be immediately investigated. Below are average login success ratios for one month of traffic across three major industries:

  • Financial institutions: 79%
  • Travel industry: 73%
  • Retailers: 62%

Individual companies deviate from this average as much as 10% – the sites where customers log in more frequently tend to have a higher login success ratio. The users at these sites are more likely to remember their passwords and are also more likely to have stored their credentials in their devices or web browsers. Banks and financial institutions only keep users logged in for 15 minutes leading to more successful logins than retailers or social media sites that keep users logged in for longer periods of time. This results in much higher login success rates for banks than for retailers.

Users also have access to few bank accounts and do not change them often, as a result they are more likely to remember their login credentials. Users however regularly shop at multiple retailers and it is easy to create a retail account. This results in lower login success rates for such sites, reflecting a higher rate of users who may be visiting for the first time in months or even years. Infrequent visitors naturally forget their passwords more regularly.

Companies should expect to see 60-85% login success rates. Anything higher or lower is suspect.

No matter the industry, companies should expect to see 60-85% login success rates. Anything higher or lower is suspect. Spikes in traffic can temporarily affect the login success ratio but those should be explainable by commonly understood events like promotions or viral marketing. If there are spikes that have nothing in common then you should look deeper, that traffic is probably a credential stuffing attack that you need to stop as soon as possible.

Graph of a customer who experienced a credential stuffing attack during a steady state of normal login successes.

One caveat

Some industries like banks and other financial institutions are frequently targets for aggregators, services like Mint and Plaid that act as delegates with user permission to log in and gather data across many companies and present it in one unified interface. Aggregators use legitimate credentials and log in multiple times a day, unnaturally inflating the login success rate. You can look for evidence of aggregators by querying for successful logins across multiple users from the same IP addresses, especially if the IP addresses are from cloud or hosting providers. This is not a foolproof method of detection but you will see traces that will help you get a better understanding of your true login success ratio. If you see login success rates in the high 80s or 90s, that is abnormally high and indicative of low credential stuffing threat but high aggregator traffic. Whether or not to consider aggregators a threat is different for every business.

Where to go from here?

What do you do if you find a login success ratio that is concerning? Like with any threat, you need visibility into the attack before you can think about mitigation. Start with free options before committing to a vendor. Tying yourself up with a vendor too early can spin you in the wrong direction and end up wasting months of time. I’ve written an article on 10 things you can do to stop credential stuffing attacks which goes over some free detection methods as well as some mitigation strategies. This should be enough to get you started understanding your problem and, once you understand the scope of your issue, then you can have better conversations with security vendors. Of course we at Shape Security are available to answer questions any time of day and you can feel free to reach out to me personally on twitter.

The Half-Day Attack: From Compromise to Cash with Sentry MBA

Sentry MBA-2

Sentry MBA, an automated attack tool used to take over accounts on major websites, makes cybercrime accessible to legions of attackers across the globe. Sentry MBA illustrates the pivotal role automation plays in online attacks and shows how cybercrime is increasingly compartmentalized and commoditized.

Allow me to illustrate with a short story.

Let’s say you’re a would-be cybercriminal looking to make some quick cash. There are many ways to make money on the Internet – especially if you think shoplifting’s a harmless recreational activity – so you hatch a plan to break into your favorite online electronics retailer’s website, order a few televisions, and have them shipped somewhere you can grab them.

But you have a problem: finding website vulnerabilities requires technical skills you just don’t possess. And even if you were a sophisticated cybercriminal, who really wants to spend their valuable time crafting SQL injection or cross-site scripting attacks? It’s far easier to just hijack a few user accounts. The authors of Verizon’s data breach report said as much: “With so many credential lists available for sale or already in the wild, why should a criminal actually earn his/her keep through SQL injection when a simple login will suffice?”

After doing some research, you may stumble across a tool like Sentry MBA. You might not have the technical expertise to research and hand-craft a targeted online exploit, but with Sentry MBA you can launch sophisticated and damaging attacks that are capable of penetrating the defenses employed by major corporations.

It’s a numbers game that works because so many people use the same passwords for multiple online accounts. Any list of stolen credentials will almost certainly include some that allow you to access accounts on the site you’ve targeted. Once you’re in, the retailer is your oyster. You can order any fancy gadget you please with the victim’s stored credit card number, change the ship-to address for your delivery convenience, and resell the goods for cash. Once you’ve maxed out one credit card, just rinse and repeat for all the accounts you cracked.

Sentry MBA automates the process of testing millions, or tens of millions, of username/password combinations to see which ones work. Without automation that task is impossibly time-consuming.

Shape Security protects websites and mobile applications by detecting and preventing automated attacks, including credential stuffing attempts. Shape analyzed a sample of our customer data consisting of six billion login and search page submissions from December of 2015 through January of 2016 and found that Sentry MBA attacks were commonplace. Here are some anonymized examples of the attacks we found:

  • Over one week in December, cybercriminals made over 5 million login attempts at a Fortune 100 B2C website using multiple attack groups and hundreds of thousands of proxies located throughout the world
  • Over two days in January, a large retailer saw two major Sentry MBA attacks with over 20,000 total login attempts
  • During one day in January, a large retailer witnessed over 10,000 login attempts used Sentry MBA and over 1000 proxies
  • Two attacks in December highlight how cybercriminals are turning their attention to mobile APIs. The first attack, focused on the target’s traditional website application, made over 30,000 login attempts using proxies located in eastern Europe. The second attack, focused on the target’s mobile API, made over 10,000 login attempts on a daily basis. Both attacks shared hundreds of IP addresses and other characteristics, indicating the same actors may have been responsible.

By reducing the level of technical skill needed to mount a sophisticated cyberattack, Sentry MBA brings damaging attacks within reach of more and more cybercriminals. The open web and darknet are filled with forums offering working Sentry MBA configuration files for specific sites and credential lists to try. These underground markets, combined with automated tools like Sentry MBA, create a new cybersecurity reality where devastating online attacks can be launched by any individual with minimal resources.

The best way to stop Sentry MBA attacks is to detect and deflect them before they take over accounts through your website or mobile application API. Shape Security protects you and your customers from online fraud committed by cybercriminals using automated attack frameworks, whether they are Sentry MBA or other toolkits.

For an in-depth exploration of Sentry MBA, please see our post from our research team: A look at Sentry MBA.

Rising Attack Vector: Credential Stuffing

Credential stuffing is a growing threat to the web community. As more companies are offering their goods and services online, customers practicing bad password hygiene are in danger of having their account stolen whenever a website is breached.

Read more about the rise of credential stuffing below.

Credential stuffing is taking lists of breached credentials from one website and testing them against another. According to the most recent Verizon Data Breach report, it’s one the fastest rising attack vectors.

The list of major companies that have fallen to this attack is impressive: Sony ‘11, Yahoo ‘12, Dropbox ‘12, and JPMC ‘14.

Credential stuffing is a general concept, but the outcome of successfully taking over user accounts results in more specific attack in various industries: stealing hotel reward points, pilfering airline frequent flier miles, and committing gift card fraud, to name just a few.

The Definition of Credential Stuffing

Credential stuffing is the automated testing of breached username/password pairs in order to fraudulently gain access to user accounts. This attack involves checking large numbers of spilled credentials against various websites to uncover credentials that are valid on a target website. Attackers then hijack those accounts and commit various types of fraud.

The Anatomy of Credential Stuffing Attack

  1. The attacker acquires spilled usernames and passwords from a website breach or password dump site.
  2. The attacker uses an account checker to test the stolen credentials against many websites (for instance, social media sites or online marketplaces).
  3. Successful logins (usually 0.1-1% of the total login attempts) allow the attacker to take over the account matching the stolen credentials.
  4. The attacker drains stolen accounts of stored value, credit card numbers, and other personally identifiable information
  5. The attacker may also use account information going forward for other nefarious purposes (for example, to send spam or create further transactions)

How is Credential Stuffing Different from Existing Threats?

We’ve classified credential stuffing as a renewed form of attack because the primary vector for account takeover has changed from the breaching of databases to automated web injection.

According to our analysis, credential stuffing is now the most popular method used by attackers to achieve account takeover. This is particularly dangerous to both consumers and enterprises because of the ripple effects of these breaches.

Credential Stuffing was the Attack Vector Used in the Sony, Yahoo, Dropbox and JPMC Breaches

Below are excerpts taken from publications analyzing these large-scale breaches. There is evidence to support that these breaches were connected by credential stuffing.

  • Sony, 2011 breach: “I wish to highlight that two-thirds of users whose data were in both the Sony data set and the Gawker breach earlier this year used the same password for each system.” Source: Agile Bits
  • Yahoo, 2012 breach: “What do Sony and Yahoo! have in common? Passwords!”. Source: Troy Hunt
  • Dropbox, 2012 breach: “The usernames and passwords referenced in these articles were stolen from unrelated services, not Dropbox. Attackers then used these stolen credentials to try to log into sites across the internet, including Dropbox”. Source: Dropbox
  • JPMC, 2014 breach: “[The breached data] contained some of the combinations of passwords and email addresses used by race participants who had registered on the Corporate Challenge website, an online platform for a series of annual charitable races that JPMorgan sponsors in major cities and that is run by an outside vendor. The races are open to bank employees and employees of other corporations”. Source: NY Times

Anatomy of the 2011 credential stuffing attack on Sony. Credentials from smaller sites are leaked and injected into Sony’s login pages to test for credential reuse. The attacker gained access to any Sony accounts which used the same credentials as were leaked from the smaller sites.

Using botnets, Sony credentials were tested on Sony’s login page. According to Wired, this resulted in 93,000 breached accounts. In other words, the credential stuffing attack that led to the Sony breach was made possible by prior breaches of smaller sites.

This connected chain of events from Sony to Yahoo to Dropbox excludes JPMC. The JPMC breach came from a separate and unrelated source. We know that the JPMC breach was caused by attackers targeting an unrelated third-party athletic race/run site for credentials to use against JPMC.

What Can SysAdmins Do to Prevent Attackers from Hijacking User Accounts by Credential Stuffing?

The answer requires an understanding of the technical mechanism by which credential stuffing works.

Like account checkers, credential stuffing works by using the static form elements of the login page as an implicit API. The attacker references various form element names (email and password) in order to interact with the target webpage. Since most websites accept such traffic as normal (having no means to distinguish between intended and malicious use), the attacker can automate the attack by using scripts and account checkers to easily run through millions of tests per unit time. Using a large-scale distributed botnet and a huge number of IP addresses allows the attacker avoid rate and volume limits which might otherwise prevent such a large number of login attempts. Thus, it is trivial even for unsophisticated attackers to launch attacks of this nature and scale against some of the largest websites in the world.

To defend websites against such activity, which we call “unwanted automation,” Shape Security uses an approach that is familiar to attackers: we dynamically change the underlying code of the site each time a page is viewed to defeat the types of scripts used in credential stuffing attacks. Just as malware authors have long used polymorphic code to evade antivirus products by constantly presenting different signatures, Shape’s solution creates a moving target which frustrates potential attackers attempting to automate easy credential testing on the website using scripts. The effort an attacker must invest to successfully automate login attempts on a given website without changing the front-end use experience.

Of course, savvy readers will point out numerous ways these measures can be circumvented. While, it is beyond the scope of this article (but perhaps the subject of future pieces) to consider such attacks (DOM, GUI, and others), Shape is keenly focused on comprehensively defeating them and has solutions at each of those levels.

Contact us to learn how Shape Security can protect your site.