Info Stealers Target Stored Browser Credentials

Typing passwords is a drag. Ever-helpful browser makers and online services know this and offer to save them for you. The problem is: Hackers know it too, only their idea is to steal the saved passwords that users have conveniently left exposed inside browsers or in cookie files.

See Also: User Entity & Behavior Analytics 101: Strategies to Detect Unusual Security Behaviors

A new report from cybersecurity firm ReliaQuest says 21% of its customers’ security incidents in 2023 that involved unauthorized credential access traced to browser credential dumping, referring to attackers stealing usernames, passwords, web browser cookies or other personal or sensitive information being stored by browsers.

To use this technique, a hacker typically uses a phishing attack or drive-by download – targeting a known vulnerability on a system – or targets a vulnerability that enables them to remotely execute code.

And for all the years of advice coming from cybersecurity professional for users not to store passwords inside browsers or not to accept “remember my details” website options, the stolen credential problem appears to be getting worse. The number of stolen logs being advertised on Russian-speaking cybercrime markets grew over the course of last year from about 150,000 to 455,000 logs, ReliaQuest says. At the start of 2023, the repositories of leaked credentials it tracks grew by 20%, from 30 billion to 36 billion credentials.

Also seen in 18% of credential-theft attacks: session-hijacking via web cookies. Such attacks involve stealing a session token, or predicting what a valid one will look like, to gain unauthorized access to a server. ReliaQuest said other credential-targeting techniques it saw “involved input capture, adversary-in-the-middle, and OS-based credential dumping techniques,” although no cases of attempted brute-force access.

Given the prevalence of such attacks, the security firm is calling on cybersecurity teams to “implement policy and control measures” designed to tackle this problem, in part by blocking employees from saving passwords in their browser, since “threat actors are accessing the storage locations and exfiltrating or decrypting the contents,” and giving them viable alternatives.

Confusing Array of Browser Options

One challenge for security teams can be knowing all of the different ways that users might be storing credentials in unsafe ways. “There is a lot of confusion about this issue,” said Ian Thornton-Trump, CISO at Cyjax.

Some browsers, including Chrome, offer a “mini-password vault,” via which they offer to pre-fill credential fields for users. Thornton-Trump likened this to having a “mini valet” with access control. These vaults don’t require two-factor authentication to access, although they could.

Such vaults differ from “remember my details” or “remember this login” prompts offered by websites. If used, these store login details, “sometimes unencrypted and unhashed,” in a cookie, “and that cookie could be stolen by someone with remote access or a keylogger,” he said.

A third type of feature is known as autofill, “which may create a cookie with sensitive information,” Thornton-Trump said. One challenge with cookies is that “protecting them is a bit difficult – it has a lot to do with web programing, including sessions and cookie expiry.” In short, whenever this feature is offered, it may not be secure.

All of these options have security shortcomings, including Chrome’s Google Password Manager. “You can’t use the Chrome browser as a password manager without a Google account,” he said. Because this inherently involves sharing passwords with a third party, doing so may well violate all manner of security policies an employee has signed.

These aren’t hypothetical concerns. Last September, Okta was hacked by an attacker who stole valid access credentials from an employee who saved them in their personal Google account while logged in on their Okta-managed laptop. The attack compromised information pertaining to every user of Okta’s primary customer support system (see: Cyber Badness: 12 Top Hacks, Data Breaches, Missteps of 2023).

Thriving Clouds of Logs

Many browser credential dumping attacks trace to information-stealing malware or Trojans. These include RedLine – used not just by criminals but also North Korea’s Lapsus group in its never-ending quest to steal cryptocurrency – as well as QakBot, ReliaQuest said. In addition, the Chinese nation-state hacking team with the codename APT31, aka Violet Typhoon and Judgment Panda, “has been known to use a Python-compiled binary with capabilities for browser credential dumping.”

A batch of information stolen from any given system is known as a log. Attackers may offer their logs for private sale, or buy, sell or distribute them via what’s known as clouds of logs (see: Info Stealers Thrive in Hot Market for Stolen Data).

These services, “available either for a small fee or free of charge, offer less-skilled threat actors initial access to data without the need for executing more challenging cybercriminal techniques like phishing and exploiting public-facing applications,” cybersecurity firm Group-IB said in a new report.

In recent months, info stealers it’s seen harvesting the greatest number of credentials, including for accessing stolen ChatGPT accounts, were LummaC2, followed by Raccoon and RedLine. Other common info stealers include Vidar, Taurus and AZORult.

Another option is Millennium-RAT, a Windows-targeting info stealer controlled via Telegram, which advertises a lifetime subscription for $30. A more powerful option is WhiteSnake Stealer, which can harvest and compress data from Windows systems and send it to a Telegram bot, and which costs $200 per month to rent.

Innovation remains constant. In June 2023, a new stealer called MacStealer debuted, offering similar capabilities for targeting macOS devices, including stealing “documents, browser cookies and login credentials,” it said.

Used by Ransomware and APT Groups

Security experts have connected info stealers to all manner of cybercrime, including stolen cryptocurrency wallet credentials being used to drain victims’ crypto accounts.

Ransomware groups and nation-state hackers also are cloud log enthusiasts, experts warn. “Attacks can look simple and victims may seem as if they are chosen at random, which leads to many people mistakenly underestimating the threat posed by information stealers to corporate networks,” Group-IB said.

Working from home and the use of employee-owned devices appear to have compounded the risk of browser credential dumping. “What’s more, sometimes employees share devices with other people,” such as their children, “which increases the risk of accidental infection through unsafe websites, games, game cheat codes and more,” Group-IB says. “Running one malicious file is enough for criminals to collect and exfiltrate all the authentication data on the device to their servers.”

Recommended Defenses

Given the risk posed by browser credential dumping, experts recommend security teams keep detailed logs, monitor for signs of info stealers, and enforce multifactor authentication wherever possible to combat attempts to use stolen credentials.

To cut down on such attacks, also “enforce policies that block users from storing credentials in the web browser,” while providing alternative functionality such as single sign-on for ease of use, ReliaQuest advised.

For protecting passwords and ensuring users only pick unique passwords, moving them to stand-alone password managers protected by two-factor authentication remains the gold standard, Cyjax’s Thornton-Trump said. “A totally separate app to manage passwords for any app and in-browser, protected by 2FA, certainly is going to be more robust just because of the 2FA alone, and then extending the password management capabilities to things like RDP connections,” he said.

For combating credential-seeking malware, ReliaQuest recommends using Active Directory group policies together with software such as AppLocker or Windows Defender Application Control, to “restrict the execution of unknown and unexpected applications that aren’t required for business use,” via an “allowlist” approach. “This will help combat the execution of info stealers by threat actors looking to extract browser credentials and telemetry data.”