You may or may not be a part of an organization that spends millions on firewalls, zero trust architecture, and EDR. But the truth is, that may not matter. That’s because many breaches no longer require a perimeter to breach. Attackers aren’t breaking in, they’re logging in.
Credential-based attacks, increasingly powered by infostealer malware, are reshaping how initial access is gained. These aren’t zero-days or brute-force campaigns. They’re quietly stolen logins, session cookies, and system fingerprints, harvested invisibly and sold at scale. The most alarming part? Most organizations never know they’ve been compromised until after the damage is done.
In this blog, we trace how infostealers extract and weaponize credentials, what happens to that data, and how those same credentials are used in real-world attacks — from account takeovers to ransomware deployment.
How are credentials stolen by infostealers used in attacks?
Infostealer infections don’t just compromise one user. They fracture the trust boundary of your entire environment. These lightweight, data-harvesting tools siphon everything from usernames and passwords to session tokens, autofill records, device fingerprints, and browser history. But the real risk begins after the exfiltration.
Once stolen, credentials enter the cybercrime economy. They’re packaged, indexed, and sold — often within hours — on underground marketplaces. What may appear as a minor endpoint infection can become the entry point for business email compromise (BEC), SaaS hijacking, or full-blown ransomware.
The infostealer supply chain: from infection to exploitation
The lifecycle of a stolen credential begins with device-level infection — often through phishing, malvertising, or rogue software. But what happens next is far more industrialized.
Infostealers like RedLine, Raccoon, and Lumma send logs to attacker-controlled command-and-control (C2) servers. From there, the data — including valid credentials, session tokens, IP and OS metadata, and even clipboard content — is organized and monetized.
Many logs are passed to initial access brokers who specialize in monetizing exposure. These brokers sell access via dark web platforms like Russian Market or Genesis. Often, these logs are indexed and searchable by domain, geography, software, or email provider. In effect, they become searchable a la carté access to organizations with no hacking required.
And it’s not just passwords that matter. Session tokens are gold. If a victim was logged into a corporate dashboard, CI/CD pipeline, cloud console, or comms platform at the time of infection, those tokens can be replayed to impersonate the user, and even bypass MFA.
Real-world exploitation scenarios
1. Account takeover (ATO)
Infostealer logs containing corporate credentials are a fast path to impersonation. One compromised user can unlock:
- Email and calendar access
- Slack, Teams, or Zoom environments
- Project tools like Jira or Notion
- Remote access via VPN or RDP
Organizations use multiple SaaS products that could potentially be compromised. Because these platforms are interconnected through SSO, OAuth, and session persistence, a single log can unlock dozens of downstream systems.
2. Business email compromise (BEC)
Once an attacker controls a corporate email account, they observe. They learn payment cycles, contracts, and communication patterns. Then they strike by impersonating finance or leadership to initiate fraudulent transfers, modifying invoices or supplier details, or even intercepting sensitive discussions for financial or strategic gain.
Because they operate from a legitimate account and familiar device profile, these attacks easily bypass phishing filters and MFA — making them especially difficult to detect.
3. Admin and developer access abuse
Infostealers don’t discriminate, and often can infect the devices of people with privileged access in your network. If an engineer or admin is infected, attackers can gain:
- Access to private GitHub or GitLab repos
- Cloud console credentials (AWS, Azure, GCP)
- Build automation tools like Jenkins or CircleCI
- Access keys and environment secrets
With these privileges, attackers can insert backdoors, deploy cryptominers, or even wipe systems, all without ever triggering a perimeter alert.
Why this matters to security teams
Infostealers aren’t just another form of malware. They’re an access-as-a-service enabler. And they bypass many traditional controls. By impersonating legitimate users, they slip past MFA through token reuse, avoid detection from traditional endpoint security, and turn “compromised credentials” into active, authenticated access.
In a recent study of 100+ enterprises, 64% had at least one known infostealer infection. Over half of those had more than five. Most occurred on unmanaged personal devices far outside the visibility of the SOC.
The takeaway: infostealer infections aren't hypothetical. They're already happening, and their downstream consequences are unfolding invisibly.
What you can do about infostealers
Security teams need to treat infostealer infections not just as alerts, but as urgent breach indicators. That means:
- Monitoring for leaked credentials and stealer logs across dark web marketplaces
- Validating which credentials are still exploitable
- Revoking access and rotating credentials at scale
- Educating users on risks associated with unmanaged devices and software downloads
- Reducing token lifetimes and expanding session control
You can follow our full remediation guide to learn step-by-step instructions on how to rid your network of an infostealers threat. The cost of doing nothing is clear: credentials harvested today can become breaches tomorrow.
