Skip to main content

What Are Infostealers?

· 5 min read
Paige Haines
Paige Haines
Cyber Capability, Education, and Training Consultant
Infostealers Thumbnail

Threat actors have shifted their focus from large-scale ransomware attacks to more subtle and persistent threats. One that you may have seen on news sites or on LinkedIn are infostealers. This post dicusses hwo these malicious programs are designed to discreetly harvest sensitive data from an infected system.

How Infostealers Operate​

Info-stealers typically operate in a four-stage process[1]: delivery, data collection, data exfiltration, and data distribution. Each phase helps the attacker successfully obtain and commercialise stolen information.

Delivery Stage​

The first step is delivery and this defines how the info-stealer finds its way into a target system. Any weak point in a system can lead to the network being popped. Attackers use several methods to execute delivery, including:

  • Phishing emails containing malicious attachments or links.
  • Drive-by downloads from compromised or fake websites.
  • Cracked software or “free” downloads that secretly contain malware.
  • Malvertising, where malicious ads redirect users to exploit kits.

Once the payload is delivered, it’s obfuscated or encrypted to bypass your traditional antivirus and endpoint protection tools. The info-stealer will subsequently discreetly install itself in the background, unbeknownst to the user.

Data Collection​

Once active, the malware begins collecting information. Common targets include:

  • Saved passwords from browsers and applications.
  • Cookies and session tokens that can allow account hijacking.
  • System information, such as OS version and hardware details.
  • Clipboard data, often used to capture cryptocurrency wallet addresses.

Some advanced info-stealers may be able to take desktop screenshots or record keystrokes (keylogging) to capture even more of your data (anything and everything is valuable to these people!).

Data Exfiltration​

After gathering sensitive information, the malware moves into the exfiltration stage where it sends the data back to the threat actor. This may occur over encrypted channels to evade detection with common techniques including:

  • Using HTTP(S) POST requests to attacker-controlled servers.
  • Uploading data via FTP or Telegram bots.
  • Storing information temporarily in cloud storage or paste sites before retrieval.

Data Distribution​

The final phase is data distribution, where the stolen information is monetised. The stolen data might be:

  • Sold on dark web marketplaces in bulk credential dumps.
  • Used directly for fraud, account takeovers, or identity theft.
  • Shared among threat actors for further exploitation or phishing campaigns.

For cybercriminals, info-stealers provide a high return on investment as there are likely low risk, quick profits, and a steady stream of usable credentials.

The Impact of Infostealers​

The consequences of info-stealers are significant not only for individuals but also for entire organisations.

For end-users this can manifest into compromised accounts (email, banking, social media), financial loss and identity theft, and straight up privacy invasion and potential reputational damage.

For organisations, this takes the form of unauthorised access to internal systems, data breaches leading to compliance violations (such as GDPR, or HIPAA), financial and operational disruptions, and brand and trust erosion if employee credentials are leaked.

Both end-users and organisations should pay attention to the above indicators of compromise (IoCs) which will allow you to act proactively before any repercussions are observed.

So, How Can I Protect Myself?​

Protecting against info-stealers requires a mix of technical controls, user awareness, and policy enforcement. Effective measures in protecting against infostealers that you may want to consider implementing include:

1. Strengthening your browser and system security by:​

  • Blocking malicious or unauthorised extensions in Microsoft Edge and Google Chrome using Group Policy or Intune.
  • Disabling password saving and credit card autofill in your browser to limit stored sensitive data.
  • Disabling automatic downloads to prevent silent malware installation.
  • Always using secure connections (HTTPS) to protect data in transit.

2. Harden endpoint protections by:​

  • Blocking Credential Stealing from LSASS (via Attack Surface Reduction - ASR) to prevent malware from extracting stored credentials.
  • Blocking script-based execution (ASR) to stop malicious PowerShell, VBScript, or JavaScript from running.
  • Enforcing an Account Lockout Policy to prevent brute-force or credential-stuffing attacks.

3. Strengthen authentication by:​

  • Enabling Multi-Factor Authentication (MFA) across all key accounts (Gmail, Outlook, WhatsApp, and others).
  • Disabling browser password managers, opting instead for a secure, standalone password manager with encryption.

4. Policy and awareness by:​

  • Regularly training users to recognise phishing attempts and suspicious downloads.
  • Monitoring for unusual login activity or credential reuse across systems.
  • Keeping systems, browsers, and plugins up to date to patch known vulnerabilities.

My Final Thoughts!​

Info-stealers are one of the fastest-growing threats at the moment, and they are all over our news timelines. Their stealth, simplicity, and profitability make them a favorite among threat actors but awareness and preventive action can dramatically lower your exposure. Good cyber security hygiene coupled with modern security tools make it significantly harder for attackers to exploit stolen information.

Your data is your most valuable asset, so protect it as such!

[1] CTM360, “Report | june 2025, infostealers: Whats stolen today may compromise your future tomorrow,” 2025. [Online]. Available: https://www.ctm360.com/reports/info-stealers-report