Infostealers are malware designed to extract access from infected devices by stealing login credentials, session tokens, and browser-stored data. They don’t lock systems or damage files. Instead, they silently collect data and upload it to a remote server, where it is packaged and sold on criminal marketplaces. Infostealers are often delivered through cracked software, phishing emails, or malicious ads. The stolen data is used by threat actors to take over accounts, bypass MFA, and pivot into corporate environments. Unlike ransomware or spyware, infostealers leave few traces. They run briefly and don’t require persistence to be effective though some variants establish persistence later. Most evade antivirus and EDR tools entirely. That makes them one of the fastest-growing and most under-detected cyberthreats in 2025.