FOG Decryption Tool

For systems compromised by FOG ransomware, a potential solution has emerged: the FOG Decryptor. Our specialized software tool is designed to decrypt files and servers affected by FOG ransomware.

FOG Decryptor Functions

Our FOG Decryptor tool employs advanced decryption techniques and has a connection to specialized online servers to circumvent the encryption mechanisms used by the ransomware:

1. Server-Based Decryption: The tool requires an active internet connection to access servers capable of calculating the necessary decryption keys. These servers exploit known weaknesses in the ransomware’s encryption algorithms, facilitating the decryption process.
2. User-Friendly Interface: Designed with ease of use in mind, the decryptor features a simple, step-by-step interface that allows users to initiate the decryption process without requiring advanced technical expertise.
3. Safety and Efficacy: Unlike generic third-party tools that may risk data corruption, the FOG Decryptor is specifically tailored for FOG ransomware, ensuring a safe and accurate decryption process.
4. Availability: The decryptor is offered as a paid tool, available for purchase by contacting the development team via email or WhatsApp.

If any issues arise during the decryption process, remote support via tools like Anydesk or similar remote access solutions is available from our support team.

Video Guide:

Although the ransomware’s binary (1.exe) lacks integrated exfiltration mechanisms, FOG operators use third-party tools to steal sensitive data during attacks, employing a tactic known as double extortion, FOG Ransomware appends .FOG, .FLOCKED, .FFOG file extension on the compromised files. Victims are pressured to pay the ransom under the threat of their stolen data being leaked on the attackers’ Data Leak Site (DLS). This article provides a deep dive into FOG’s tactics, techniques, and procedures (TTPs), as well as a comprehensive technical analysis of its ransomware payload, which has proven to be highly disruptive and destructive.

FOG ransomware is a rising threat that has rapidly made a name for itself by aggressively targeting the education sector in the U.S. The group emerged in May 2024 and has shown a unique specialization in breaching educational institutions, primarily through exploiting compromised VPN credentials. Once inside, FOG operators focus on privilege escalation, system reconnaissance, and deploying their ransomware payload to encrypt critical data.

The group’s double extortion tactics involve not only encrypting data but also threatening to leak it unless the victim pays a ransom, often exceeding $220,000 in initial demands. Although relatively new, FOG’s growing impact on the education sector warrants a detailed examination of its attack patterns, methods, and technical structure.

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Key Targets

FOG ransomware’s primary targets are higher educational institutions in the United States. From April to July 2024, over 70% of the group’s victims have been from the education sector, making FOG one of the few ransomware groups specifically focusing on this industry.

The reason for targeting educational institutions lies in their often outdated cybersecurity practices, reliance on open networks for students and faculty, and the large volumes of sensitive data they hold. These factors make them attractive targets for ransomware groups like FOG, which can inflict significant damage and increase pressure on their victims to pay large ransoms.

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Initial Access (& command-and-control (C2)

The FOG ransomware group typically gains initial access to a target’s network through compromised VPN credentials or valid user account credentials. These compromised credentials are often obtained through phishing attacks or brute-force attacks on remote desktop protocol (RDP) services.

Once inside, FOG operators leverage these credentials to navigate through the network without raising alarms. Their ability to bypass traditional security protocols stems from the use of legitimate login details, making it difficult for security systems to distinguish between normal activity and malicious intent.

In ransomware attacks, threat actors often use such legitimate remote access tools to establish command-and-control (C2) communication. The use of such services not only complicates the identification of malicious activities but also enables attackers to leverage existing infrastructure, rather than having to implement their own.

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Privilege Escalation

After gaining access to the network, FOG operators focus on escalating privileges. This is often achieved by employing pass-the-hash attacks, where attackers use a hashed version of a password to gain unauthorized access to other systems.

Other privilege escalation techniques observed include:

• Brute forcing of user accounts, especially those with administrative access.
• Extracting passwords stored in user browsers or from the NTDS.dit file, which contains Active Directory credentials.
• Custom PowerShell scripts are deployed to automate the collection of these credentials.

These methods allow the attackers to gain control over high-level administrative accounts, giving them unrestricted access to sensitive parts of the network.

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Persistence Mechanisms

To maintain persistence within the target’s network, FOG ransomware operators establish Remote Desktop Protocol (RDP) connections on Windows servers. These connections are maintained even after the initial intrusion by:

• Hijacking additional user accounts through credential stuffing (re-using passwords across different accounts).
• Creating new user accounts solely for the purpose of maintaining access.
• Employing tools like FileZilla and reverse SSH shells to ensure a foothold on the compromised system.

By setting up these backdoors, FOG can maintain prolonged access to the network, allowing them to carefully deploy their ransomware and carry out exfiltration before encrypting files.

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Enumeration Techniques

Once inside the network, FOG operators carry out extensive reconnaissance to identify high-value targets for encryption. They utilize a combination of tools, such as:

• Metasploit and PsExec for moving laterally across the network.
• Advanced Port Scanner, LOLBins (Living off the Land Binaries), SharpShares, and SoftPerfect Network Scanner to gather intelligence on the network’s structure and connected devices.

By mapping out the network, FOG ensures that they can encrypt critical data and disrupt the victim’s operations.

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Evasion Tactics

FOG ransomware is skilled in evasion tactics that allow them to bypass security measures and prevent detection. On compromised Windows servers, attackers:

• Disable Windows Defender and other security processes.
• Terminate specific services using Windows API calls to avoid detection.
• Deploy their ransomware once these defenses have been neutralized.

FOG also deletes Veeam backups and Windows Volume Shadow copies, which hinders the victim’s ability to recover encrypted files.

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Ransomware Deployment

FOG’s ransomware payload encrypts a wide variety of files, including Virtual Machine Disks (VMDKs). After encryption, the ransomware appends file extensions such as .FOG, .FLOCKED, or .FFOG to the affected files.

The ransomware leaves behind a ransom note named “readme.txt”, which provides instructions for the victim to pay the ransom. The note includes a link to a Tor-based negotiation site, where the victim can discuss the ransom and view proof of stolen files.

Before encryption, the malware ensures the deletion of shadow copies using the command:

Bash: vssadmin.exe delete shadows /all /quiet

This prevents the victim from recovering their data through built-in Windows recovery options.

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Exfiltration Methods

Although the FOG ransomware binary itself lacks direct exfiltration mechanisms, attackers use third-party tools such as 7-Zip, WinRAR, and cloud services to exfiltrate sensitive data before deploying the ransomware.

FOG operators have been observed leveraging cloud services like MEGAsync to transfer stolen data, often leading to double extortion tactics. If the ransom is not paid, the attackers threaten to publish the stolen data on their Data Leak Site (DLS), colloquially known as the Fog Blog.

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Ransom Demands

FOG ransomware ransom demands can vary depending on the size and resources of the targeted organization. In many cases, initial ransom demands are as high as $220,000, but negotiation often leads to a median payment of around $100,000.

If you are reading this, then you have been the victim of a cyber attack. We call ourselves Fog and we take responsibility for this incident. You can check out our blog where we post company data: xbkv2qey6u3gd3qxcojynrt4h5sgrhkar6whuo74wo63hijnn677jnyd.onion You might appear there if you opt out of our communication.

We are the ones who encrypted your data and also copied some of it to our internal resource. The sooner you contact us, the sooner we can resolve this incident and get you back to work.
To contact us you need to have Tor browser installed:

1. Follow this link: xql562evsy7njcsngacphc2erzjfecwotdkobn3m4uxu2gtqh26newid.onion
2. Enter the code: [snip]
3. Now we can communicate safely.

If you are decision-maker, you will get all the details when you get in touch. We are waiting for you.

The ransomware operators utilize a Tor-based chat interface for negotiations, where victims can view encrypted data and negotiate payment terms. FOG’s use of double extortion means that victims who do not pay the ransom face the risk of their stolen data being publicly leaked.

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Malware Analysis

Upon execution, the FOG ransomware binary (e.g., 1.exe) creates a DbgLog.sys file in the directory from which it was launched. This log file contains valuable debugging information that tracks the malware’s execution and system interactions.

The malware also queries system information such as available drives and processors, allocating threads accordingly for efficient encryption. The encryption process is handled via symmetric encryption, with the generated key then encrypted using an asymmetric key, making decryption impossible without the attacker’s private key.

Key features of the malware include:

• File encryption using AES with a configurable block size.
• Command-line flags such as nomutex, procoff, and target for customization.
• The deletion of shadow volumes to prevent recovery via the vssadmin command.

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Technical Analysis

The technical configuration of FOG ransomware provides multiple customizable options, allowing attackers to modify the encryption process. Some key configurable values in the malware’s JSON configuration file include:

• RSAPubKey: The RSA public key used for encrypting the symmetric key.
• LockedExt: The file extension added to encrypted files (.fog, .ffog, or .flocked).
• NotefileName: The name of the ransom note (typically “readme.txt”).
• ShutdownProcesses and ShutdownServices: The processes and services to terminate before encryption.

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Incident Response Statistics

According to data from Arete’s Incident Response team, 36% of engagements involving FOG ransomware included data exfiltration. The median initial ransom demand was $220,000, and the median payment facilitated was $100,000.

Common tools used by FOG during these incidents included CobaltStrike, Mimikatz, ngrok, and AnyDesk, among others.

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Defensive Recommendations

To defend against FOG ransomware, organizations should implement the following measures:

1. Strengthen VPN Security: Ensure VPN credentials are regularly rotated and protected with multi-factor authentication (MFA).
2. Monitor for Privilege Escalation: Deploy endpoint detection and response (EDR) tools to identify abnormal account activity.
3. Backup and Recovery: Implement robust backup policies that include offline, air-gapped backups and frequent backup testing.
4. Patch Management: Keep all software, including VPNs and remote access tools, up-to-date to prevent exploitation of known vulnerabilities.

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FOG ransomware represents a growing and highly disruptive threat, particularly to the education sector. Its focus on double extortion, sophisticated privilege escalation techniques, and the use of third-party tools for exfiltration make it a formidable adversary. Organizations, especially in the education sector, must strengthen their defenses and be vigilant against this evolving cyber threat.