How do infostealers typically spread to user devices?

Infostealers commonly spread through phishing emails and social engineering tactics, tricking users into clicking malicious links or opening infected attachments. They can also be distributed via malicious downloads disguised as legitimate software, SEO poisoning, malvertising, and drive-by downloads from compromised websites.

What are some common infostealer families mentioned?

Several prominent infostealer families include LummaC2, known for its rapid updates, and RedLine Stealer, a long-standing threat often used in phishing campaigns. Other notable families are Vidar, which is flexible and used in multi-stage attacks, StealC, designed for stealth, and Raccoon Stealer, popular for its simplicity, along with the legacy tool Agent Tesla.

How can I tell if my device has been infected with an infostealer?

A key indicator is finding your corporate credentials on dark web marketplaces shortly after they were potentially harvested. Unusual login activity on cloud and SaaS platforms, especially from unknown locations or devices, is another strong sign. Monitoring for abnormal outbound traffic to services like Telegram or Dropbox can also help detect data exfiltration attempts.

What are the best practices to avoid infostealer infections?

Always be cautious about downloading files, opening attachments, or clicking links from untrusted sources. Avoid downloading cracked or unofficial software, as these are common vectors for infostealers. Using phishing resistant authentication methods like FIDO2 or passkeys adds a significant layer of protection.

Infostealers: The Cyber Threat Behind Today’s Biggest Data Breaches

Q: What exactly are infostealers and what do they steal?

Infostealers are a type of malware designed to steal sensitive information from infected devices. This data can include saved passwords, browser cookies, session tokens, cryptocurrency wallet details, and autofill information. The stolen credentials are often used as a gateway for more significant cyberattacks.

In recent years, a relatively simple form of malware has been used as a launching point for large-scale, targeted cyberattacks. Infostealers are a category of malware designed to harvest sensitive information from infected devices. This includes saved passwords, browser cookies, session tokens, cryptocurrency wallet details, autofill information, and sometimes even files stored on the system. According to Flashpoint, these stealthy credential-stealing tools were linked to the theft of over 1.8 billion credentials in 2025, from about 5.8 million infected devices. A separate December 2025 study by DeepStrike reported 1.8 billion credentials compromised across 5.8 million affected devices, an 800% increase compared to previous years. The stolen credentials are often used as a starting point for ransomware attacks, business email compromise schemes, and account takeover fraud.

How Infostealers Spread

This remains the most common method. Attackers send deceptive emails or messages with malicious links or attachments. A sophisticated variant, known as "ClickFix," tricks users into copying and pasting a malicious PowerShell command into their terminal, often disguised as a CAPTCHA verification.

Malicious Downloads

This includes "trojanised" software, such as a fake installer for a popular program, distributed through malvertising or typo-squatted domains.

SEO Poisoning and Malvertising

Cybercriminals manipulate search engine results or place malicious ads to direct users to fake download sites for popular tools, which then infect the user's system.

Drive-by Downloads

Simply visiting a compromised or malicious website can trigger an automatic download of the infostealer without the user's knowledge

Common Infostealer Families

Lumma (LummaC2)

A highly dominant Malware-as-a-Service stealer known for fast updates and wide distribution. It targets browser credentials, cookies, crypto wallets, and messaging sessions, and is often delivered through fake downloads or malicious websites.

RedLine Stealer

One of the longest-running infostealers. It is widely used in mass phishing and cracked-software campaigns to steal passwords, browser data, FTP/VPN credentials, and crypto wallets. Even after takedowns, new variants continue to circulate.

Vidar

A flexible and long-lived stealer often used in multi-stage attacks. It focuses on browser session cookies, saved credentials, and crypto wallets, and is sometimes paired with ransomware campaigns for follow-up exploitation.

StealC

A lightweight, modular infostealer designed to be stealthy and adaptable. It mainly targets browsers, Discord tokens, and cryptocurrency wallets while minimizing detection by security tools.

Raccoon Stealer (v2)

A re-emerged Malware-as-a-Service stealer that quickly returned after a major takedown. It is popular due to its simplicity and focuses heavily on browser-stored passwords and financial data.

Agent Tesla (still active legacy tool)

Originally a keylogger/RAT hybrid, it still appears in credential theft campaigns. It captures keystrokes, clipboard data, and stored passwords, especially in phishing-based attacks.

How to know if you have an Infostealer Infection

One of the earliest warning signs is the appearance of corporate credentials on dark web marketplaces. Stolen usernames, passwords, and session data are frequently uploaded to cybercriminal markets within hours of being harvested. Continuous monitoring for exposed company email addresses and domain credentials can help organizations identify compromised users before attackers escalate their access. Unusual login activity across cloud and SaaS platforms is another strong indicator. Authentication attempts from unfamiliar locations, previously unseen devices, or concurrent sessions originating from different regions may suggest that stolen session cookies or authentication tokens are being used. Organizations should also monitor for abnormal outbound traffic to services commonly abused for data exfiltration. Connections to platforms such as Telegram, Dropbox, GitHub, or other cloud-based services from endpoints that do not normally communicate with them can be a red flag, especially when accompanied by file archiving, compression, or other data staging activities that may indicate information is being prepared for theft.

Why Infostealers Are Growing Rapidly

One of the drivers behind the surge in infostealer activity is the growth of the malware-as-a-service (MaaS) ecosystem. Infostealers are inexpensive to deploy, easy to scale, and can generate high profits for cybercriminals. Instead of developing their own attack infrastructure, many threat actors purchase ready-made stealer malware, loaders, or initial access services from underground marketplaces. This lowers the technical barriers to entry, enabling even relatively inexperienced attackers to launch large-scale credential theft campaigns. This division of labor is a major reason why infostealers remain such a persistent threat. Malware operators can quickly update their code, switch infrastructure, and launch new campaigns with little effort, while affiliates focus on spreading the malware through phishing emails, malvertising, fake software downloads, and social media scams. This streamlined model allows campaigns to scale rapidly and adapt to disruption with ease. At the same time, advances in evasion techniques make infostealers difficult to detect. Many use fileless execution, in-memory payload delivery, and process injection to avoid signature-based security tools.

Best Practices for Minimizing Infostealer Exposure

Be Cautious

Since infostealers are designed to extract personal data by exploiting user behavior, it is important to avoid downloading files, opening email attachments, or clicking links from unknown or untrusted sources without first carefully verifying the sender.

Avoid high-risk downloads

Refrain from using cracks, unofficial software, and dubious "free premium" tools. These are among the most common vectors for stealer distribution.

Isolate risky activities

Keep high-value accounts, such as banking, corporate systems, and cryptocurrency wallets, on a separate Windows profile or device from the one you use for downloading and testing unknown game modifications or files.

Adopt phishing-resistant authentication methods.

FIDO2 and passkey systems create unique cryptographic credentials for each service, with private keys remaining securely stored on the user's device. As a result, compromising one service does not expose reusable login data, since there are no shared password secrets to steal or reuse elsewhere.

Infostealers: The Cyber Threat Behind Today’s Biggest Data Breaches