While ransomware tends to dominate headlines, a quieter class of malware has taken centre stage in 2024: infostealers. Lightweight and insidious, these malware variants are designed not to destroy systems, but to silently extract sensitive information, and they’ve become foundational to today’s cybercrime operations.

As the broader cybercriminal ecosystem has matured and specialized, infostealers have grown in both sophistication and impact. Today, they serve as the first step toward full-scale corporate network breaches, bridging the gap between low-effort infections and high-value access.

What Are Infostealers and How Do They Work?

Infostealers are a class of malware designed to extract browser-stored credentials, session cookies, crypto wallets, system information, and even screenshots. Once executed (usually through phishing, malvertising, or cracked software), they quietly exfiltrate data to remote servers, often within minutes. The infection may go unnoticed by users, making detection difficult and response delayed.

Their success lies not just in their technical efficiency, but in their widespread deployment. Many campaigns rely on a spray-and-pray approach, compromising personal devices that are then used to access corporate systems. Recent research shows that more than 70% of infostealer infections affect personal, unmanaged endpoints – a critical risk in BYOD environments.

From Logs to Ransomware: Why They’re So Dangerous

Infostealers play a crucial role in the cybercrime chain. They don’t cause immediate destruction, but they enable devastating follow-up attacks. Stolen credentials are used for account takeovers, VPN intrusions, and identity spoofing. Alarmingly, 90% of breached companies had credentials leaked in infostealer logs before the actual breach occurred.

One of the most valuable assets harvested by stealers is session tokens. These allow attackers to bypass login credentials entirely, often evading MFA protections. If sold while still valid, tokens provide immediate access to accounts and cloud services.

This data is then sold through underground markets and Telegram channels, often for just $10 per log, fuelling financial fraud, identity theft, and ransomware campaigns – all part of a thriving cybercriminal ecosystem.

The Infostealer-as-a-Service Economy

Infostealers operate through the Malware-as-a-Service (MaaS) model. Threat actors, or affiliates, can easily purchase access to tools like RedLine, StealC, or Lumma for a monthly fee – typically between $150 and $250. In return, they receive technical support, updates, and user-friendly control panels for managing campaigns and processing stolen data.

Logs are automatically sorted, classified, and delivered through real-time dashboards or Telegram bots. This level of automation allows attackers to rapidly exploit stolen session tokens, credentials, and financial data – sometimes within minutes of infection.

In parallel, Initial Access Brokers (IABs) play a key role by buying these logs, identifying valuable targets, and reselling access to ransomware affiliates. It’s a fully operational supply chain, with infostealers acting as the entry point to large-scale breaches.

How Companies Can Defend Themselves

Combating infostealers requires more than antivirus – it demands visibility, speed, and coordination. A modern Security Operations Center (SOC) becomes essential to orchestrate detection, response, and contextual analysis.

SIEM and EDR/XDR platforms detect unusual behaviours – for example, unexpected browser activity or outbound traffic to known C2 infrastructures. However, detection alone isn’t enough. Companies need cross-layer observability, allowing them to correlate endpoint telemetry with identity, network, and cloud behaviour. This makes it possible to flag infections early, before stolen credentials are exploited.

Additionally, enforcing stronger BYOD policies, securing browser storage, and improving session management (e.g. token expiration, cookie revocation) are critical steps to limit exposure – particularly as many infostealer infections begin on personal, unmanaged devices.

Organizations should also focus on tightening access controls, ensuring that corporate systems and SaaS platforms are only reachable from trusted, compliant devices. Restricting access based on device posture can significantly reduce the chances of a compromised endpoint leading to wider exposure.

Finally, user awareness remains one of the most effective lines of defense. Training employees to recognize phishing attempts, malicious downloads, and fake software update prompts helps reduce infection vectors before they even reach technical controls.

A Threat That Fuels the Entire Ecosystem

Infostealers don’t cause chaos on their own, but they pave the way for it. The Snowflake breach in 2024, affecting over 165 organizations, is suspected to have started with credentials leaked through infostealer logs.

Their role in the cybercrime economy is foundational, enabling access, accelerating intrusions, and powering entire criminal supply chains. As they become faster, more automated, and easier to deploy, their real danger lies not in what they steal, but in what they set in motion.

In an increasingly interconnected threat landscape, understanding infostealers means understanding how modern attacks begin. And that’s the first step toward stopping what comes next.

Data source: THE STATE OF CYBER SECURITY 2025, Check Point