Fog Ransomware: The Silent Storm in Cyber Extortion

A new threat has emerged—stealthy, persistent, and far more dangerous than previous ransomware strains. Fog Ransomware, discovered in mid-2024, has swiftly gained notoriety for its ability to paralyze entire organizations through advanced infiltration techniques and a double-extortion model.

This isn’t just another headline. Fog is a wake-up call: it shows how modern ransomware campaigns are no longer brute-force attacks but carefully orchestrated operations, targeting sectors that once flew under the radar and exploiting the most overlooked vulnerabilities.

Let’s break down how it works, who’s at risk, and—most importantly—how to defend against it.

🧠 What Sets Fog Ransomware Apart?

Fog doesn’t follow a predictable pattern. Instead, it adapts, hiding in plain sight and launching when defenses are down.

Its dual-encryption approach—using both AES and RSA—renders decryption almost impossible without the private key. Combined with stealth-based execution, it bypasses most traditional antivirus systems with ease.

Fog employs several techniques that make it highly evasive:

• 🧬 Fileless Execution: Operates entirely in memory, leaving no trace on disk.
• 🌀 Code Obfuscation: Alters its own code to avoid signature-based detection.
• 🛑 Disables Security Tools: Turns off Windows Defender and similar protections silently.
• 🎭 Abuses Legitimate Tools: Mimics user behavior using PowerShell and WMI scripting.

These tactics make Fog a prime example of modern ransomware-as-a-service (RaaS): agile, stealthy, and scalable.

🎯 Who’s in the Crosshairs?

Initially, education and recreation sectors were Fog’s main targets—industries with low IT budgets and minimal monitoring. But that’s changing.

Recent patterns show opportunistic expansion:

• 🔓 Finance
• 🔓 Technology
• 🔓 Healthcare

No sector is truly safe, especially as attackers leverage credential leaks and unpatched VPNs to scale their reach.

⚠️ Real-World Damage Beyond Encryption

The impact of a Fog attack can ripple through an organization, halting operations and eroding trust.

Here’s what victims face:

• 🔒 Critical system disruption
• 💸 Ransom costs + revenue loss from downtime
• 📉 Reputational damage among customers and partners
• ⚖️ Regulatory pressure if security negligence is uncovered

Fog’s use of double extortion—encrypting files and threatening to leak sensitive data—adds urgency and psychological pressure, forcing faster payments and larger sums.

🔄 The Fog Infection Lifecycle: 4 Phases

Understanding how Fog moves can help organizations detect and stop it early.

1️⃣ Exploitation & Entry

• Targets VPN vulnerabilities like CVE-2024-40766 in outdated SonicWall devices
• Also leverages stolen credentials from previous data breaches

2️⃣ Lateral Movement

• Uses tools like BloodHound, AnyDesk, and pass-the-hash techniques
• Maps internal networks and escalates privileges quietly

3️⃣ Deployment & Encryption

• Disables defenses and backup systems
• Encrypts VMDK files and appends .FOG or .FLOCKED extensions

4️⃣ Extortion Phase

• Drops readme.txt ransom notes with communication instructions
• Threatens public data leaks if payment isn't made quickly

This lifecycle can unfold in hours or days, depending on system defenses.

🔍 Common Entry Points and Vulnerabilities

Fog ransomware doesn’t rely on one method—it exploits the weakest links:

• 🔓 Unpatched VPN firmware, especially SonicWall devices
• 🔑 Credential reuse from previous data breaches
• 🔁 Unmonitored remote access tools like AnyDesk or TeamViewer

Organizations that delay patching or fail to track user access are especially vulnerable.

🛡️ How to Defend Against Fog Ransomware

A reactive approach won’t work. Fog requires layered defense strategies that combine awareness, technical controls, and operational discipline.

✅ Key Mitigation Strategies

• User Awareness Training: Educate staff to spot phishing attempts and spoofed logins
• Isolated Backups: Keep encrypted, offline copies of critical data
• Patch Management: Regularly update all VPNs, endpoints, and internal tools
• Phishing-Resistant MFA: Apply strong multi-factor authentication, especially for admins
• Network Segmentation: Restrict lateral movement across systems
• Honeypots & Decoy Files: Plant bait files and track access from known VPS or threat actors

It’s not about one silver bullet—it’s about consistent visibility, vigilance, and layered controls.

📣 Final Thoughts: Don’t Wait for the Fog to Set In

Fog ransomware isn’t just another malware strain. It’s part of a new wave of AI-aware, stealth-based cyber extortion tactics—designed to strike where it hurts most: trust, uptime, and critical data.

Every organization, regardless of size or sector, should be asking:

Are we ready to detect and contain an attack like this? Is our VPN patched? Are our backups isolated? Is our team trained?

If the answer isn’t a confident yes, now is the time to act.

🔍 Stay Ahead of Ransomware Threats

At Peris.ai Cybersecurity, we help organizations proactively assess vulnerabilities, strengthen endpoint defenses, and train teams to recognize ransomware threats before they escalate. From threat detection to rapid response—resilience starts here.

👉 Visit peris.ai for tools, threat insights, and protection strategies tailored to your business.