Fog Ransomware: Inside the Double-Extortion Malware Targeting Windows and Linux Systems

Fog ransomware is a sophisticated malware strain that uses a double extortion strategy, combining file encryption with data theft to maximize pressure on victims. Organizations not only face locked systems but also the threat of having sensitive data leaked publicly if ransom demands are not met.

First identified in mid-2024, Fog has rapidly evolved to target both Windows and Linux environments, significantly expanding its reach compared to traditional ransomware threats. Its cross-platform capabilities and aggressive tactics have made it one of the fastest-growing cyber threats in the past year.

Industries most affected by Fog ransomware include healthcare, education, manufacturing, and the financial sector — sectors where operational downtime and data exposure carry especially high risks. As its attack methods continue to mature, Fog ransomware represents a major concern for businesses across critical infrastructure and service industries.

What Is Fog Ransomware?

Fog ransomware follows a double extortion strategy designed to maximize pressure on victims. After breaching a network, Fog operators first steal sensitive files — including financial records, internal communications, and customer data — and then encrypt the local copies to disrupt operations. Victims face two options: pay the ransom or risk public exposure of the stolen information, along with the operational downtime caused by encryption. This tactic ensures that even organizations with good backups are still at risk of reputational and regulatory damage.

The group behind Fog has automated much of this process, streamlining both the exfiltration and encryption phases to minimize the time between initial compromise and ransom demand, often completing the operation in under a few hours.

File Encryption Behavior: .fog, .Fog, and .FLOCKED Extensions

Fog ransomware exhibits a distinct encryption behavior that security teams can use for early detection. When encrypting files, Fog appends one of several extensions to affected files:

• .fog – The most commonly used extension.
• .Fog – Capitalized version observed in some targeted attacks.
• .FLOCKED – A newer extension variant associated with later campaigns starting in early 2025.

The choice of extension may depend on the targeted operating system or the ransomware build used for the campaign. In all cases, Fog typically encrypts user documents, databases, VM disk images, and system backups, while avoiding critical system files needed for basic boot functionality to ensure the victim can still see the ransom note.

TOR-Based Leak Site and Victim Pressure

To further coerce payment, Fog operators maintain a dedicated leak site on the TOR network. Organizations that refuse to negotiate within the given timeframe are listed publicly, often accompanied by small samples of the stolen data as proof.

The leak site has several key features:

• Countdown timers indicating when full data dumps will be published.
• Victim profiles outlining stolen data types (e.g., “HR files,” “Customer contracts,” etc.).
• Downloadable sample files to intensify pressure and create fear of broader leaks.

This strategy not only damages a victim’s public image but may also trigger compliance violations under regulations such as GDPR, HIPAA, and PCI-DSS, depending on the nature of the leaked data.

Cryptocurrency-Based Ransom Demands

Fog demands payment exclusively in cryptocurrencies, favoring Monero (XMR) for its superior transaction privacy. In some campaigns, Fog also accepts Bitcoin (BTC) but usually at a higher ransom amount to account for Bitcoin’s lower anonymity.

Negotiations occur over private TOR-based chat portals unique to each victim. The ransom demand amount is often calculated based on:

• Organization size and revenue.
• Criticality of exfiltrated data.
• The success or failure of initial attempts to restore from backups.

Fog operators often apply escalating threats during negotiation, such as raising the ransom or accelerating the release of stolen files, to force quicker payments.

How Fog Ransomware Attacks: Step-by-Step Breakdown

How Fog Ransomware Gains Initial Access

Fog ransomware operators employ a combination of social engineering and technical exploitation methods to establish their initial foothold:

• Phishing Emails: Attack campaigns often begin with carefully crafted phishing emails containing malicious ZIP attachments, such as Pay Adjustment.zip or Invoice Update.zip. These archives typically contain a loader executable disguised as a PDF or Excel file, which, when opened, downloads and installs the Fog malware.
• Exploitation of Public-Facing Applications: In parallel, attackers scan for vulnerable services exposed to the internet, particularly Remote Desktop Protocol (RDP) and VPN appliances. Common entry points include systems lacking multifactor authentication (MFA) or running outdated software with known vulnerabilities.
• Stolen Credentials from Initial Access Brokers (IABs): Fog operators also purchase compromised login credentials from darknet marketplaces. These credentials often come from previous breaches or successful phishing operations and are used to access corporate VPNs, RDP sessions, or SaaS management consoles without raising immediate suspicion.

What Happens After Fog Ransomware Gains Initial Access: Privilege Escalation and Persistence

Once inside the environment, Fog operators move quickly to escalate privileges and establish persistence:

• Credential Dumping with Mimikatz: The attackers deploy Mimikatz, a widely known post-exploitation tool, to extract plaintext passwords, hashes, and Kerberos tickets from memory. This allows them to pivot laterally or escalate their privileges to domain admin level.
• BYOVD Attack with Ktool.exe: Fog has been observed leveraging a Bring Your Own Vulnerable Driver (BYOVD) technique using Ktool.exe. This tool installs a known-vulnerable kernel driver, then exploits it to disable endpoint security solutions, giving attackers near-total control over the compromised system.
• Registry Modifications and Scheduled Tasks: To maintain persistence, Fog modifies Windows Registry keys to autorun their payloads after system reboots. They also create scheduled tasks disguised under benign names (e.g., “Windows Update Checker”) that periodically relaunch the ransomware or its loaders.

Lateral Movement of Fog Ransomware

With administrative access secured, Fog spreads laterally through the network to maximize its impact:

• Remote Desktop Protocol (RDP): Attackers use legitimate RDP connections to move between systems, blending into normal administrative traffic.
• Server Message Block (SMB): Through SMB shares, Fog operators copy malicious payloads across different systems.
• PsExec and PowerShell Scripts: Fog utilizes Sysinternals PsExec to execute binaries remotely and PowerShell scripts like Lootsubmit.ps1 and Trackerjacker.ps1 to automate the discovery and compromise of additional machines, domain controllers, and file servers.

These tools and techniques allow the operators to spread rapidly while evading traditional network security monitoring.

Data Exfiltration and Encryption

Once Fog has a broad footprint in the environment, it begins its final and most damaging phases:

• Data Exfiltration: Sensitive data is staged and exfiltrated using tools like Rclone, configured to send files to attacker-controlled cloud storage. In some cases, direct uploads to remote FTP servers over encrypted channels have been observed.
• File Encryption Mechanics: Fog encrypts files using a hybrid model:
  • AES-256 is used for encrypting individual files quickly.
  • RSA public-key cryptography secures the AES keys, preventing decryption without the attacker’s private key.

The malware carefully terminates specific services and processes to avoid interference during encryption. For instance, it shuts down Volume Shadow Copy Service (vssadmin.exe) to eliminate potential backup recovery options before encryption begins.

• Process Targeting: In virtualized environments, Fog actively kills hypervisor-related services, virtual machine disk processes (e.g., .vmdk, .vhd), and database services to ensure maximum disruption.

Ransom Demand

After encryption is complete, Fog initiates its extortion phase:

• Delivery of Ransom Notes: A file named readme.txt is dropped in every encrypted directory. The note provides instructions for accessing a victim-specific TOR portal to begin ransom negotiations. Victims are typically given 5–7 days to respond before data is published or sold.
• TOR Negotiation Portals and Threats: Victims interact with the operators over TOR-hidden chat services where ransom amounts are discussed. Threats escalate with time:
  • Leak of stolen data samples.
  • Complete data dumps.
  • Public “naming and shaming” on Fog’s TOR leak site.

Operators often increase the ransom amount if deadlines are missed and can adjust the terms dynamically based on how negotiations proceed.

Technical Deep Dive: How Fog Ransomware Operates

Fog ransomware uses a variety of advanced techniques to efficiently propagate, encrypt, and extort from its victims. Below, we will break down the command-line parameters Fog utilizes and how the malware aligns with MITRE ATT&CK tactics to better understand its behavior.

Fog Ransomware Command-Line Parameters

Fog ransomware operates with several command-line parameters that are integral to its functionality and flexibility. These parameters allow the operators to customize the attack based on the specific environment they are targeting, ensuring the malware behaves as intended while avoiding detection or interference. Here are some key parameters observed in Fog’s execution:

• –offvm: This parameter is used to ensure that Fog ransomware will not attempt to run on virtual machines (VMs). This is a precautionary measure to avoid running into issues when infecting virtualized environments, as some virtual machines might have different security controls or configurations that could interfere with the malware’s payload.
• –processallfiles: This command forces Fog to scan and encrypt all files it encounters, regardless of their type or location on the system. This aggressive approach maximizes the damage by ensuring that no file is left unencrypted. It can also slow down the malware’s operation, but the attackers prioritize making the system completely unusable to pressure the victim into paying the ransom.
• –thread: This command specifies the number of threads (parallel processes) Fog can run simultaneously. The use of multiple threads accelerates the encryption process, allowing the malware to affect more files in a shorter amount of time. This is particularly important in large enterprise environments, where data volumes are substantial, and speed is critical to inflict maximum disruption quickly.

MITRE ATT&CK Techniques Utilized by Fog Ransomware

Fog ransomware closely aligns with several tactics outlined in the MITRE ATT&CK Framework, which is a globally recognized model for describing the actions and behaviors of adversaries during cyberattacks. Understanding these techniques helps defenders better anticipate and prepare for attacks like Fog ransomware.

• Phishing (T1566): Phishing is the primary method for initial access in Fog’s attack chain. The ransomware operators use deceptive emails with malicious attachments (e.g., ZIP files) to trick users into executing the malware. Once the attachment is opened, it triggers the download of the full ransomware payload. The attachment is often disguised as a legitimate business document, such as an invoice or pay adjustment notification.
• Obfuscation (T1027): To evade detection by security tools, Fog ransomware utilizes obfuscation techniques. This involves making the ransomware’s code and behavior harder to analyze by antivirus solutions. For example, the executable payloads may be encrypted, compressed, or disguised within benign-looking files, such as PDF or Excel files, making them harder for traditional signature-based defenses to identify.
• Data Encryption (T1486): Once inside the system, Fog ransomware deploys data encryption as its primary extortion tactic. The malware uses AES-256 encryption to lock files and then employs RSA public-key encryption to protect the encryption keys. This ensures that only the attackers can decrypt the files. Fog is efficient in its encryption process and terminates backup services (e.g., Volume Shadow Copy Service) to prevent recovery from backups, leaving the victim with limited options for data restoration.

By utilizing these techniques, Fog ransomware can spread quickly, exfiltrate data, and encrypt systems before its activities are detected, resulting in a devastating impact for organizations that fall victim to it.

Impact of Fog Ransomware and Known Targets

Fog ransomware has had a significant impact across various sectors, exploiting vulnerabilities in widely-used systems and causing widespread disruption. Its reach has extended to several industries, with financial and operational consequences for its victims.

Sectors Targeted by Fog Ransomware

Fog ransomware has primarily targeted industries where sensitive data and operational continuity are crucial. The sectors most affected by this threat include:

• Finance: Financial institutions are prime targets for ransomware attacks due to the wealth of sensitive financial data they hold, including customer information, transaction records, and internal financial systems. Fog ransomware has shown a particular affinity for these organizations, likely because the ransom demands can be higher given the financial implications of an attack.
• Education: Universities, schools, and educational institutions, often with outdated systems or limited security resources, have been frequent victims. The exposure of research data, student information, and administrative systems presents a lucrative target for attackers.
• Manufacturing: Manufacturers are also at risk, with Fog targeting critical infrastructure and proprietary designs. The ransomware can disrupt production lines, delay shipments, and affect supply chains, creating significant operational losses.
• Transportation: Fog ransomware has impacted the transportation sector, targeting systems managing logistics, fleet operations, and customer data. A disruption in transportation systems can lead to widespread delays and operational gridlocks, increasing the pressure on companies to comply with ransom demands.

Notable Incidents Involving Fog Ransomware

Fog ransomware has made headlines in several high-profile attacks, demonstrating the increasing sophistication of these cybercriminal operations:

• Thwarted Attack on a Financial Business (August 2024): In August 2024, a targeted attack on a financial services company was successfully mitigated before any significant data was stolen or encrypted. However, the attempt highlights the growing trend of financial organizations being specifically targeted by Fog ransomware operators. This case also emphasizes the importance of early detection and strong defenses against ransomware threats.
• 53 Organizations Attacked (February 2025): In February 2025, a large-scale campaign attributed to Fog ransomware targeted 53 organizations across multiple industries. These attacks affected both public and private sector entities, showcasing the versatility and widespread nature of the ransomware. As organizations continue to face evolving threats, the February 2025 campaign serves as a stark reminder of the persistence of Fog ransomware in various markets.

Average Victims per Month of Fog Ransomware

On average, between 18 and 29 organizations fall victim to Fog ransomware each month. This statistic underscores the rapid spread of this malware, as well as the consistent threat it poses to organizations of varying sizes and across different sectors. The number of victims highlights the effectiveness of Fog’s distribution methods, including phishing campaigns, exploitation of public-facing services, and stolen credentials, which continue to be successful in bypassing traditional defenses.

The impact of Fog ransomware is felt not just in terms of financial losses but also in reputational damage, data loss, and recovery efforts. Organizations in its path face prolonged operational disruptions, the risk of data exposure, and the ongoing threat of further extortion through leaked data. As Fog ransomware continues to evolve, it is essential for organizations to enhance their cybersecurity posture to prevent falling victim to such damaging attacks.

Fog Ransomware Associated Malware and Tools

Fog ransomware does not operate in isolation. Its campaigns often involve a collection of associated malware, custom-built tools, and attack techniques that work together to maximize disruption and complicate incident response efforts. Understanding these associated components is critical to fully appreciating the technical sophistication of Fog operations.

Links to STOP/DJVU Ransomware Variant

Fog shares notable code similarities with the STOP/DJVU ransomware family, one of the most widespread and persistent ransomware variants in the wild. Analysts have observed overlapping encryption routines, payload obfuscation methods, and ransom note formats between Fog and STOP/DJVU samples. Additionally, both malware families use similar techniques to terminate security processes and evade detection, suggesting either code reuse, collaboration between threat groups, or evolution from a common malware toolkit. While Fog introduces its own enhancements — such as more aggressive lateral movement and enterprise-targeted payloads — the foundational influence of STOP/DJVU is evident in its underlying structure.

Use of Linux Payloads to Attack VM Disks

Fog ransomware has evolved beyond traditional Windows environments. Operators deploy Linux-based payloads specifically crafted to target and corrupt virtual machine (VM) disk files. These payloads seek out virtual disk formats like .vmdk (VMware), .vhd (Hyper-V), and .qcow2 (KVM) within hypervisor storage environments. Once located, the Linux payloads either encrypt or overwrite these disk files, rendering critical business infrastructure unusable. This cross-platform capability demonstrates Fog’s intent to maximize damage, especially in organizations heavily reliant on virtualized environments for business continuity. By expanding attacks to the virtualization layer, Fog can cripple entire fleets of servers with a single successful infiltration.

Loader Tools: cwiper.exe and stage1.ps1

The Fog infection chain frequently employs custom loader tools designed for stealthy payload delivery and execution:

• cwiper.exe: This Windows-based executable acts as a file wiper and loader. Upon execution, cwiper.exe attempts to disable endpoint protection services and prepares the environment for ransomware deployment. It may also delete system logs and forensic artifacts to hinder post-incident investigation efforts.
• stage1.ps1: A PowerShell script that serves as the first-stage downloader. Stage1.ps1 establishes outbound connections to attacker-controlled servers to retrieve secondary payloads — typically the main Fog ransomware binary or additional lateral movement tools. The script is obfuscated to evade signature-based detection and often uses living-off-the-land (LOTL) techniques, abusing built-in Windows utilities to minimize its footprint.

The combined use of executable loaders and PowerShell-based downloaders gives Fog operators flexibility in targeting different environments while maintaining operational security. This layered approach complicates detection and prolongs dwell time, allowing attackers to fully prepare the target environment before executing the final ransomware payload.

Overall, Fog’s use of recycled ransomware techniques, cross-platform payloads, and modular toolchains highlights the growing trend of professionalization among ransomware groups. Their technical depth demands equally advanced detection, prevention, and response strategies from defenders.

Recent Tactical Shifts and Unique Traits of Fog Ransomware

Fog ransomware continues to evolve, adopting new tactics that distinguish it from other ransomware operations and make it increasingly difficult for organizations to defend against and recover from attacks.

Publishing Victim IPs on the Dark Web

One of the more recent shifts in Fog’s tactics is the public exposure of victim information earlier in the extortion process. Instead of waiting for ransom negotiation deadlines to pass, Fog operators have started publishing the external IP addresses of compromised organizations on Dark Web leak sites within hours of attack execution. This aggressive move acts as a psychological weapon, immediately signaling to victims — and the broader criminal underground — that a breach has occurred. By outing victims early, Fog creates additional pressure to pay quickly and deters attempts to delay negotiations or quietly recover from backups without paying ransom. In some cases, even incomplete exfiltrations or failed encryption attempts still resulted in victim exposure, showcasing Fog’s shift toward a name-and-shame-first extortion strategy.

Dogecoin-Themed Ransom Notes with Monero QR Codes

Another unique trait of Fog ransomware is its peculiar ransom note design. While most modern ransomware groups adopt a strictly professional or threatening tone, Fog inserts a layer of mockery by delivering ransom notes heavily themed around Dogecoin memes — using Doge imagery, casual internet slang, and references to “wow much crypto, very secure.” Despite the seemingly playful surface, the payment mechanism remains serious: embedded within the notes are QR codes linked to Monero (XMR) wallets. The use of Monero, a privacy-focused cryptocurrency known for its resistance to tracking, complicates ransom payment tracing for law enforcement and cybersecurity firms. This blend of humor and operational security suggests an intent not only to taunt victims but also to delay investigative efforts through misdirection.

Rapid Encryption Capabilities

Fog ransomware also stands out for its extremely fast encryption routines. In optimized test environments, full encryption of a medium-sized corporate network has been observed in under two hours. Several design choices contribute to this speed:

• Multithreading Support: Fog’s encryption engine utilizes the –thread command-line parameter to spawn multiple encryption threads per host, maximizing CPU utilization and reducing encryption time dramatically.
• Selective Targeting: Rather than encrypting every file indiscriminately, Fog prioritizes high-value directories such as shared drives, database repositories, and user document folders, allowing it to cripple operations while avoiding unnecessary delays.
• Process Termination: By terminating competing services (e.g., database engines, hypervisor processes) before encryption, Fog ensures file locks do not slow down access and encryption rates.

This rapid encryption capability gives defenders little time to detect, respond, or interrupt an active attack. Organizations relying solely on manual monitoring or delayed detection tools are particularly vulnerable to total environment compromise within a very short window.

In combining early victim exposure, psychologically manipulative ransom notes, and high-speed attack execution, Fog ransomware exemplifies the next generation of ransomware tactics: faster, more aggressive, and more tailored to destabilize victims emotionally and operationally.

How to Defend Against Fog Ransomware

Fog ransomware’s speed, multi-vector entry tactics, and persistence mechanisms demand a layered and proactive defense strategy. Standard antivirus and signature-based defenses alone are insufficient against a threat that leverages legitimate tools and advanced obfuscation. Organizations must implement technical controls and monitoring practices designed specifically to counter ransomware campaigns like Fog.

Prioritize Patching of Known Vulnerabilities

Many Fog ransomware intrusions begin with the exploitation of unpatched, internet-exposed services such as VPN appliances and RDP gateways. Timely patching is critical. Vulnerability management programs must prioritize:

• External Attack Surfaces: Ensure that any system exposed to the internet — VPNs, firewalls, web applications — is up to date with vendor security patches. Delay in patching known vulnerabilities like RDP flaws (e.g., BlueKeep CVE-2019-0708) or VPN vulnerabilities (e.g., Pulse Secure CVEs) provides Fog operators with easy initial access points.
• Third-Party Software: Routine patching must extend beyond core OS updates to include middleware, remote management tools, and third-party plugins often overlooked in audits.
• Virtualization and Backup Infrastructure: Given Fog’s targeting of hypervisors and backup processes, ensuring that vCenter servers, hypervisors (e.g., VMware ESXi, Hyper-V), and backup software are hardened and patched is equally important.

Patching should be automated where possible and prioritized based on CVSS scores, weaponization status, and public exploit availability.

Monitor RDP and SMB Traffic for Anomalies

Fog’s lateral movement phase relies heavily on Remote Desktop Protocol (RDP) sessions, Server Message Block (SMB) shares, and administrative tools like PsExec. Continuous network monitoring is essential to detect suspicious behaviors before encryption begins:

• Unusual RDP Connections: Monitor for RDP login attempts from atypical source IP addresses, at irregular hours, or using non-standard accounts. Brute-force detection mechanisms and GeoIP filtering can help block unauthorized access.
• Excessive SMB File Transfers: Set up alerts for mass file copy operations over SMB, particularly those targeting backup locations or administrative shares.
• Lateral Tool Usage Detection: Flag internal use of PsExec, remote PowerShell commands, and scripts like Lootsubmit.ps1, which Fog has used to automate network discovery and compromise.

By correlating authentication logs, session data, and traffic patterns, defenders can spot lateral movement activities early and isolate affected machines before full network compromise.

Deploy Behavioral Detection and Advanced Endpoint Protection

Fog ransomware frequently employs customized loaders (e.g., cwiper.exe, stage1.ps1), BYOVD (Bring Your Own Vulnerable Driver) attacks, and heavily obfuscated payloads. These methods often bypass traditional signature-based detection. To counter them:

• Behavioral Analysis Engines: Deploy security tools that detect unusual behavior — such as mass file modifications, registry persistence attempts, suspicious driver installations, and service tampering — rather than relying solely on known malware signatures.
• Endpoint Detection and Response (EDR): EDR platforms capable of kernel-level monitoring can detect BYOVD techniques like the use of vulnerable drivers (e.g., with Ktool.exe) to disable antivirus or EDR agents themselves.
• Application Control and Sandboxing: Implement application allowlisting to prevent unauthorized executables from running, particularly from user profile directories or temporary folders, where Fog loaders often stage their payloads.

Combining these controls with 24/7 monitoring and incident response readiness ensures that even if initial defenses fail, security teams can respond quickly to contain Fog’s activities before irreversible damage occurs.

How to Prevent a Successful Fog Ransomware Attack

Stopping Fog ransomware before it causes irreversible damage requires a defense-in-depth strategy that addresses both detection and recovery. Given Fog’s advanced techniques — including credential theft, lateral movement via legitimate tools, and rapid encryption — organizations must combine proactive threat hunting with resilient data protection practices.

Deploy Advanced Threat Detection and Response Solutions

Fog ransomware’s operators are highly skilled at using legitimate administrative tools (e.g., PsExec, PowerShell scripts) to blend in with normal activity. Traditional security solutions often fail to detect such abuse until it’s too late. Therefore, deploying Endpoint Detection and Response (EDR) and Extended Detection and Response (XDR) solutions is critical.

• EDR/XDR Capabilities: Look for platforms that provide real-time telemetry across endpoints, servers, and cloud environments. Critical features include memory analysis, detection of living-off-the-land (LOTL) techniques, and behavioral anomaly detection — such as sudden mass file modifications or unexpected service terminations.
• Early Intrusion Identification: These solutions can spot the use of tools like Mimikatz (for credential dumping) and abnormal privilege escalation attempts tied to the BYOVD technique Fog operators favor.
• Software-Based Deployment: 365GDR is an excellent option for organizations looking to quickly deploy a software-driven threat detection and response system. It integrates seamlessly with existing environments and provides comprehensive endpoint visibility, behavioral analytics, and automated containment capabilities.
• On-Prem Security Appliance Option: For organizations preferring a dedicated on-premises solution, the SA365 Security Appliance offers powerful EDR/XDR functionality in a hardened platform, combining real-time monitoring with network-level threat detection and automated response features.

Organizations should integrate EDR/XDR alerts with their security operations center (SOC) for rapid triage and incident response.

Maintain Regular Air-Gapped and Immutable Backups

Recovery without paying a ransom is only possible if clean data backups exist — and those backups must be resilient against attacker tampering. Fog ransomware actively targets backup services and shadow copies during its encryption stage to sabotage recovery efforts.

• Air-Gapped Backups: Maintain copies of critical data completely disconnected from production networks — either via offline storage media or isolated network segments with no direct route from compromised environments.
• Immutable Storage: Backups should be stored on systems that support immutability, ensuring that once written, backup data cannot be altered or deleted, even by users with administrative rights. Technologies like WORM (Write Once, Read Many) file systems, object-locking in S3-compatible storage, or dedicated immutability settings in backup software are essential.
• Backup Validation: Regularly test backup restoration procedures to verify that backups are not only accessible but also uncorrupted and current.

Having air-gapped, immutable backups drastically reduces the impact of Fog ransomware, transforming a potential business-ending event into a manageable recovery operation.

Monitor for Credential Theft, Lateral Movement, and Data Exfiltration

Fog’s attack chain heavily depends on the theft of credentials and stealthy lateral movement before encryption begins. Early detection of these behaviors can prevent widespread impact.

• Credential Monitoring: Analyze authentication logs for anomalies, such as credential use from unusual IP addresses, logins during odd hours, or access patterns inconsistent with normal user behavior.
• Lateral Movement Detection: Set up alerts for PsExec usage, remote PowerShell sessions, RDP brute-force attempts, and SMB traffic spikes — all indicators of an active ransomware operator moving through the network.
• Data Exfiltration Monitoring: Fog operators often exfiltrate sensitive data before encrypting it, using tools like Rclone or direct FTP uploads. Monitor outbound network traffic for signs of large, encrypted data transfers to external IPs, particularly cloud storage services not approved for business use.

Deploying network detection and response (NDR) tools alongside EDR/XDR solutions can enhance visibility into these behaviors, providing the early warnings necessary to contain Fog before encryption begins.

Conclusion

Fog ransomware represents a sophisticated and evolving threat, leveraging stealthy techniques, rapid encryption capabilities, and disruptive extortion tactics to maximize damage. Its use of living-off-the-land tools, targeted attacks across critical industries, and Dark Web data leaks demand a multi-layered defense strategy.

Organizations must prioritize proactive threat detection with advanced EDR/XDR platforms like 365GDR, or consider deploying hardened security appliances like the SA365 for on-premises protection. Equally important is maintaining frequent, air-gapped, and immutable backups to ensure that even if initial defenses are breached, recovery remains possible without succumbing to ransom demands.

By combining early intrusion detection, behavioral monitoring, and resilient backup strategies, businesses can significantly reduce their exposure to Fog ransomware and maintain operational continuity against even the most aggressive attacks.