Infostealers: The Silent Threat Compromising the World One Password at a Time

Explore how Infostealers compromise global security, silently stealing data and offering adversaries initial access.
advisory Infostealers feature image

Table of Contents

What Are Infostealers?

Infostealers are a class of malicious software designed to collect and exfiltrate data from systems or networks without user consent. These stealth programs, often driven by financial or criminal motives, aim to exfiltrate sensitive information, posing significant risks to both individuals and organizations.

The first observed modern infostealer dates back to early 2007 and was known as ZeuS or Zbot. The main objective of the malware was to steal online banking credentials and quickly became one of the most widespread and sophisticated banking trojans ever seen. In 2011, the source code was publicly released, leading to the proliferation of numerous new variants.

Over the years, technological advancements and the underground economy have facilitated the development and proliferation of new infostealer variants, with cybercriminals continuously improving their tactics to evade detection and maximize profits. Today, infostealers remain a prevalent and potent threat, posing serious risks to individuals, businesses, and organizations worldwide. 

Increasingly, infostealers are being used as an entry point in sophisticated cyber attacks, underscoring their role as a fundamental threat vector in modern cybercrime.

How Do Infostealers work?

The main function of an infostealer is to clandestinely collect sensitive information from victims through various techniques such as enumerating files and directories, logging keystrokes, extracting browser data, accessing files, copying cookies and taking screenshots. The stolen data is then transmitted to a command and control server controlled by the attacker.

As is common with modern malware, infostealers have transitioned to a Malware as a Service (MaaS) model. This facilitates attackers with minimal expertise in targeting companies by utilizing such services to infiltrate systems and extract information, often in the format of logs. Subsequently, these logs are sold on underground forums and criminal marketplaces on the dark web.

Data most frequently targeted by infostealers:

  • System Configuration information
  • Account credentials
  • Browser data such as cookies and extension data
  • Credit cards
  • Crypto wallets
  • Autofill information

Infostealers are distributed over several channels including phishing, spread phishing, and malvertising. Additionally, uncommon distribution methods include SEO Poisoning, fake software, and public social network posts. 

Common Distribution Channels

Phishing: This Is a common method of distributing several malware families, usually cybercriminals send documents such as PDFs, HTML files, or those from MS Office containing malicious payloads or camouflaged URL links to download the artifacts. To try to evade detection, files are often encrypted with passwords, rendering it challenging for email providers to scan for malicious content.

Legitimate software instrumentation: This is a classic infection vector, users can be easily infected when installing illegitimate software. Modified versions often harbor embedded malicious code, making them a significant risk to inexperienced users.

Malversiting: This trend started while back in 2017 and is currently on a surge, malicious actors distribute malicious payloads through some high-rank pages, oftentimes impersonating updates for popular software, like Google Chrome. 

The Infrastructure Behind an Infostealer Botnet

The following is the topology of Redline Stealer, a typical modern infostealer. conducted by Jiho Kim

Analyzing Stolen Information

The information collected by infostealers is focused on specific objectives. On one hand, it aims to acquire sensitive data like banking portal credentials, cryptocurrency wallets, email account details, social media credentials or any information that could be exploited for future misuse. On the other hand, Infostealers also gather technical details about the compromised system, including session cookies, UserAgents, machine specifications, and log files. These technical insights allow attackers to simulate the environment of targeted accounts, evading security measures and attempting unauthorized access without environmental restrictions.

Below is an example of information stolen by a real MaaS infostealer.

Most infostealers possess the capability to identify multiple login portals and extract credentials. After it, they format this information into structured logs, employing various techniques to transmit them to adversarial infrastructure (Exfiltration). This allows attackers to easily access and exploit sensitive information collected from compromised systems.

Stats from the Dark World

Source: Hudson Rock

Infostealers and the Cybercrime Economy

Behind information theft lies an intricate cybercriminal ecosystem with diverse roles and profit levels. Researchers from SecureWorks identify at least four tiers: 

Developers and Information Experts: Tasked with creating programs to steal data while evading cybersecurity measures. This level thrives on market demand for specific features tailored to targets. 

Criminal Marketplaces: The second tier, also known as Initial Access Brokers (IABs), operates on dark web forums, offering services and access ranging from $50 to $1000 USD, depending on the infostealer type. Customers, typically malicious actors leveraging industry-specific knowledge, utilize this initial access for sophisticated attacks like Ransomware. The rise of Ransomware as a Service (RaaS) has heightened the importance of IABs, streamlining intelligence gathering and reconnaissance, enabling attackers to initiate attacks with a solid initial vector.

Dark Support Infrastructure: These offshore support services are dedicated to maintaining anonymity for cybercriminals. In the latest Models as a Service (MaaS), this infrastructure is managed by the owners of the malware services themselves.

Victims: Ultimately, victims of such attacks, under pressure from various factors, succumb to paying ransom to criminal gangs. This payment is made to prevent the publication of sensitive data or decrypt crucial information essential for business continuity. Unwittingly, these actions contribute to the perpetuation of the criminal economic cycle.

There are several forums that sell information on the dark web, like 2easy, BidenCash and Russian Market. There is also a recent trend to sell that information on decentralized stores and social media platforms like Telegram & others. 

BidenCash Market

Telegram BerkserkLogs Market

Several Threat Actors have been seen using Initial Access Brokers to comrpomise networks and perform large scale attacks, like Lockbit 3.0, Royal Ransomware, BlackHunt, Medusa, & others.  

Has Your Network Been Compromised by InfoStealers?

Threat actors constantly scan the internet for fresh targets. The more information they possess about a company, the greater their possibility to infiltrate the infrastructure. Weak security measures to decrease the attack surface, enabling attackers to identify and exploit vulnerabilities effortlessly. Moreover, the ease of acquiring credentials or access to environments facilitates illicit activities, allowing malicious actors to operate easily.

At present, several companies remain unaware that multiple of their employee credentials are being sold on the dark web. Quietly, attackers hold the key to initiating large-scale attacks. 

Observe Your Network Activity

Lumu’s Continuous Compromise Assessment allows you to identify when, where, and how your infrastructure is communicating with adversaries, you gain the visibility you need of what is happening anytime in your network. The robust process of cyber threat intelligence provides you with crucial information to safeguard your infrastructure and effectively mitigate threats across multiple stages of the infection chain.

Lumu tracks malicious infrastructure that distributes, communicates or controls malware, phishing, spam, malvertising and different types of threats and techniques, and alerts your company when the enemy comes knocking.

Mitre Map of Infostealer Malware




T1589 Gather Victim Identity Information


T1598 Phishing for information

Resource Development

T1583.001 Acquire Infraestructure: Domains

Resource Development

T1585.001 Establish Accounts: Social Media Accounts

Initial Access

T1566: Phishing

Initial Access

T1204.002: Malicious File

Initial Access

T1189 Drive-by Compromise

Initial Access

T1199: Trusted Relationship

Initial Access

T1078.002 Valid Accounts: Domain Accounts


T1059.003: Windows Command Shell


T1059.001: PowerShell


T1648 Serverless execution


T1204 User execution


T1136 Create account

Privilege escalation

T1484.002 Domain Policy modification

Defense Evasion

T1564.001: Hidden Files and Directories

Defense Evasion

T1070.004 Indicator Removal File Deletion

Defense Evasion

T1578.002 Modify Cloud Compute Infraestructure

Defense Evasion

T1497.001 System Checks

Credential Access

T1555.003: Credentials from Web Browsers

Credential Access

T1555 Indicator RemovalFile Deletion

Credential Access

T1606 Forge Web Credentials

Credential Access

T1621 Multi-Factor Authentication Request Generation

Credential Access

T1552 Unsecure Credentials: Credentials in files


T1087: Account Discovery


T1217: Browser Information Discovery


T1046: Network Service Discovery


T1057: Process Discovery


T1012: Query Registry


T1518: Software Discovery


T1016: System Network Configuration Discovery


T1614: System Location Discovery: System Language Discovery


T1083: File and Directory Discovery


T1082: System Information Discovery


T1033: System Owner/User Discovery


T1538: Cloud Service Dashboard.


T1018: Remote System Discovery


T1539: Steal web session cookie


T1113: Screen Capture


T1119: Automated Collection


T1115: Clipboard Data


T1005: Data from Local System


T1056.001: Keylogging

Command & Control

T1102: Web Service

Command & Control

T1102.002: Bidirectional Communication


T1041: Exfiltration Over Command-and-Control Channel


T1020: Automated Exfiltration


T1048: Exfiltration Over Alternative Protocol

Adopt Strategies to Minimize Your Attack Surface

This silent adversary takes advantage of any inadvertent information divulged by companies. Every service that companies expose to the internet must undergo risk analysis. Companies need to adopt strategies to assess their exposed infrastructure and determine its necessity in terms of business operations. Access should be restricted using methods of least privilege in their networks and authentication systems.

The adversary will try to communicate with your infrastructure and you must be prepared to detect it.

Check Your Devices

It’s crucial to have monitoring tools in place to keep track of your device services, detecting any suspicious behavior promptly. If your company has an EDR, it is essential to maintain it up-to-date.

Protecting Against Infostealers

Cybersecurity operators looking to protect against the threat posed by infostealers can take the following actions:

  • Establish an effective strategy for the continuous monitoring of network and endpoint activity to detect any suspicious activity. 
  • Make sure that any communication between your network and adversarial infrastructure is being  blocked. With Lumu’s 125+ integrations, any detected contacts are immediately blocked using existing cybersecurity infrastructure.
  • Enforce the principle of least privilege to ensure that users have access to services and permissions for their job functions and no more.
  • Do not expose unnecessary services. Users are advised to disable their Remote Desktop protocols (RDPs) if not in use, if required, it should be placed behind the firewall and users are to bind with proper policies while using an RDP.
  • Get to know if there are compromised credentials. 
  • Familiarize employees with a proper procedure for opening digital documents 
  • Tune your spam defenses
  • Establish a Sender Policy Framework (SPF) for your domain.


The stealth and sophistication of infostealer malware present a clear and present danger to global cybersecurity. Originally designed for data theft, infostealers now provide cyber adversaries with a potent tool for initial access, thereby setting the stage for more devastating attacks. Organizations must prioritize the detection and mitigation of infostealers as part of a comprehensive cybersecurity strategy. By remaining vigilant, continuously monitoring for suspicious activity, and employing advanced threat detection and response mechanisms, we can significantly reduce the risk posed by these silent threats.

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