The Growing Threat of Infostealer Malware

Infostealer Malware Is Draining Business Credentials — Here’s How to Stop It

Threat actors no longer need to breach your perimeter to own your environment. A single infected endpoint, one careless download, or one employee who reuses a password across services can hand attackers the keys to your email, cloud apps, financial accounts, and crypto holdings. The weapon of choice: infostealer malware.

At Envescent, we see infostealers dominate incident response engagements. They are fast, cheap to deploy, and built to bypass legacy antivirus. Understanding how they work is the first step toward shutting them down.

What Infostealers Actually Do

Infostealers are a category of malware designed to exfiltrate data from compromised endpoints — quietly and quickly. Unlike ransomware, which announces itself with encrypted files and a ransom note, infostealers slip in, grab what they want, and leave almost no trace. Victims often find out weeks later, when attackers use stolen credentials to log in, move laterally, or drain funds.

The most active families today include:

• LummaC2 . A subscription-based stealer sold as malware-as-a-service (MaaS), frequently distributed through phishing pages and malvertising.
• RedLine . One of the most widely deployed stealers, often delivered through cracked software downloads and malicious email attachments.
• Raccoon . A long-standing stealer known for ease of use and broad targeting of browsers and crypto wallets.
• Vidar . A descendant of Arkei, capable of stealing browser data, FTP credentials, and cryptocurrency wallets.
• StealC . A newer, increasingly popular stealer that targets session cookies and bypasses some MFA setups.

These families share a common playbook, and their success depends on three primary data sources.

How Infostealers Steal What Matters

Credentials

Infostealers scan browsers and password stores for saved usernames and passwords. Most browsers store credentials in local SQLite databases, encrypted with keys the operating system makes accessible to the logged-in user. Once malware runs under that user’s context, it can decrypt and exfiltrate every saved credential. The same applies to credentials stored by email clients, FTP programs, and certain desktop applications.

Attackers then sell these credentials on Telegram channels and underground forums. Buyers test them against corporate VPNs, Microsoft 365, GitHub, AWS consoles, and banking portals. Reused passwords mean a single stolen credential can unlock dozens of services.

Session Cookies

Session cookies are the silent killer. When a user logs into a service, the server issues a session token stored as a cookie. As long as the cookie is valid, the user stays logged in . no password required. Infostealers grab these cookies from browser cookie stores and send them to attacker-controlled servers. Attackers then inject the cookies into their own browsers and access the victim’s accounts directly.

This matters because session cookies can defeat multi-factor authentication. The user already passed MFA when the session was established. A replayed cookie looks like a legitimate continuation of that session. StealC, LummaC2, and Vidar are all engineered to target cookies, which is why MFA alone is not enough.

Cryptocurrency Wallets

Infostealers hunt for browser extension wallets like MetaMask, Phantom, and Trust Wallet, plus desktop wallets such as Exodus and Electrum. Wallet seed phrases, private keys, and extension-stored data are exfiltrated in seconds. Once attackers have the seed phrase, they control the wallet entirely . no password reset, no recovery, no recourse.

Web3 and fintech organizations face especially high exposure, but any business holding corporate crypto assets or processing wallet-based transactions is a target.

Practical Mitigation

Defending against infostealers requires layered controls that assume endpoints will be compromised. Here is what works.

Deploy Endpoint Detection and Response (EDR)

Signature-based antivirus cannot keep up with polymorphic stealers delivered through MaaS platforms. EDR monitors process behavior, script execution, fileless attacks, and suspicious network connections. When LummaC2 tries to dump a browser’s credential store, EDR detects the behavior and isolates the endpoint before exfiltration completes.

Envescent deploys and manages endpoint protection platforms tuned for infostealer behavior. Our monitoring teams review alerts around the clock, contain infected hosts, and coordinate response before stolen data reaches criminal markets.

Enforce Multi-Factor Authentication . and Protect Sessions

MFA still matters. It blocks credential replay and slows attackers down. But pair MFA with session controls: short session lifetimes, conditional access policies, reauthentication for sensitive actions, and IP-based anomaly detection. Where possible, use phishing-resistant MFA like FIDO2 security keys, which cannot be bypassed with stolen session cookies.

Mandate Password Managers

Stop letting browsers save passwords. Enterprise password managers like 1Password, Bitwarden, and Keeper encrypt credential vaults separately from the browser, requiring a master password and typically MFA to unlock. Infostealers that target browser stores come up empty when no credentials are saved there.

Harden Browser Security

Restrict unnecessary browser extensions, block known-malicious domains through DNS filtering, disable autofill for sensitive fields, and enforce content security policies on corporate web apps. Deploy browser isolation for high-risk users who handle financial transactions or crypto wallets.

Train Employees to Recognize Delivery Vectors

Infostealers spread through cracked software, fake updates, phishing emails, and malicious ads. Train employees to avoid software cracks, verify update prompts through vendor sites, and report suspicious emails immediately. Regular tabletop exercises and phishing simulations keep awareness sharp.

What Envescent Does Differently

Envescent delivers endpoint protection and continuous monitoring designed to catch infostealers at every stage . from initial execution to attempted exfiltration. Our teams deploy EDR tuned to detect LummaC2, RedLine, Raccoon, Vidar, StealC, and emerging variants. We integrate endpoint telemetry with identity monitoring so that a stolen credential or hijacked session triggers an immediate response.

When a client endpoint flags a credential-dumping attempt, our analysts isolate the host, preserve forensic evidence, rotate affected credentials, and validate that no session cookies remain active. We close the loop . not just detect the threat.

Infostealers will keep evolving. LummaC2 operators will push new features. StealC affiliates will find fresh delivery methods. The businesses that stay safe are the ones that treat endpoint security as a continuous operation, not a one-time install.

If you want to understand your exposure and build a defense that actually stops infostealers, talk to Envescent. Schedule a consultation at https://envescent.com/contact-us.