Iranian cyber actors are using a malware family known as HEAVYGRAM, also tracked as CHOSEN BRICK, to target dissidents, journalists, and opposition groups worldwide, according to a recent FBI FLASH report and a joint advisory from the UK National Cyber Security Centre (NCSC), the US FBI, and the Netherlands' General Intelligence and Security Service (AIVD). The FBI assesses that the malware is deployed on behalf of the Government of Iran's Ministry of Intelligence and Security (MOIS) to collect intelligence, conduct data leaks, and cause reputational harm to targets. The joint advisory adds that Iran almost certainly uses cyber activity to support repression of individuals seen as threats to the regime.

Who Is Being Targeted by Iranian Cyber Actors

The victim profile includes Iranian dissidents, journalists opposed to Iran, members of organizations with views countering Government of Iran narratives, and other individuals the Iranian government perceives as threats. The joint advisory notes that CHOSEN BRICK has been used against individuals in the UK, US, and Netherlands since at least 2025, and that personal details of some victims have appeared on pro-Iranian leak sites, increasing risks to their personal safety. In some cases, Iranian intelligence services have plotted to kidnap or conduct lethal operations against individuals abroad who are seen as enemies of the regime.

Social Engineering and Delivery

Iranian cyber actors rely heavily on social engineering to deliver their malware. Actors communicate with targets through platforms such as Telegram, WhatsApp, and Instagram, often posing as individuals known to the target or as technical support from the messaging platform. The joint advisory notes that actors research targets in advance to appear credible, and often initiate contact through a target's work device before shifting to personal devices if the initial delivery attempt fails or risks detection. Victims are persuaded to download files disguised as legitimate applications, including Pictory, RunwayML, Norton Antivirus, Telegram, Adobe Flash Player, and KeePass, or files appearing to be MRI scan results. The FBI notes that some victims downloaded AnyDesk and provided access strings, while others downloaded malware masquerading as a program installer. The malware targets only the Windows operating system.

Persistence and Telegram Command and Control

Once installed, the malware achieves persistence by adding registry keys, most often within the Run key at HKCU\Software\Microsoft\Windows\CurrentVersion\Run, so it runs automatically at user login. It also adds exclusions to Microsoft Defender antivirus to evade detection. The malware then connects to Telegram command-and-control infrastructure, with each victim device linked to a unique Telegram Bot ID to prevent cross-contamination between victims. Through Telegram, the malware can enumerate running processes and system information, capture screen content, enable the microphone to record audio, copy Telegram and WhatsApp data from browsers, download additional files, delete files, steal email content, and wipe the computer system. Files and data are exfiltrated through the Telegram bot and cloud object stores such as VultrObjects and StorjShare. Recent variants use HTTPS/SOCKS5 proxies to obscure the use of Telegram bots.

FBI Recommendations

The FBI recommends caution regarding communications from unknown individuals, keeping devices updated, downloading software only from trusted sources, enabling antivirus software, using strong unique passwords with multi-factor authentication, and reporting suspicious messages. The NCSC, FBI, and AIVD jointly recommend phishing-resistant multi-factor authentication, application allowlisting, email scanning security features, and endpoint and network monitoring. Organizations concerned about a potential HEAVYGRAM or CHOSEN BRICK infection are advised to contact their IT providers and check both corporate and personal devices, since the actors also target individuals outside their workplace systems.

Gunra ransomware has expanded its operations through a structured ransomware-as-a-service (RaaS) affiliate program, prompting the FBI, CISA and other agencies to issue a joint advisory warning organizations about the threat. The Gunra ransomware variant uses a double-extortion model, encrypting victim data while threatening to publish stolen information on a dedicated leak site if ransom demands are not met. The FBI first observed Gunra in April 2025 as a double-extortion ransomware variant derived from leaked Conti ransomware source code.

Gunra Ransomware Shifts to Affiliate Model

By early 2026, the group had expanded through a formal ransomware-as-a-service affiliate program advertised on dark web forums. The program provides affiliates with a management panel, configurable ransomware builder, cross-platform locker payloads and affiliate documentation. The FBI also observed Gunra operating under new branding aliases, including Golden Community, while recruiting penetration testers and ethical hackers as initial access brokers. Gunra initially focused on Windows environments before introducing a Linux variant and moving toward broader cross-platform targeting. Victims observed on the group’s dedicated leak site include organizations across the Americas, Europe, the Middle East, Africa and the Asia-Pacific. Targeted sectors include healthcare and public health, financial services and insurance, critical manufacturing, transportation, government services, utilities, academia, media and communications, retail, and professional and nonprofit services.

VPN Vulnerabilities Used for Initial Access

According to the advisory, Gunra actors primarily gained initial access by exploiting known vulnerabilities in internet-facing devices, including firewall and VPN gateways. The FBI observed exploitation of CVE-2024-55591 and CVE-2025-24472, authentication bypass vulnerabilities affecting specific FortiOS and FortiProxy versions. The Republic of Korea’s National Police Agency also observed Gunra actors exploiting credential exposure and SSH access control weaknesses in internet-facing VPN gateways to obtain unauthorized remote access. After gaining access, attackers used tools including Impacket utilities to move laterally through victim networks using SMB. In one case, actors compromised an SSL-VPN appliance using default credentials where account lockout controls were absent. They later used stolen session information to access internal virtual desktop infrastructure and move through systems including Active Directory servers and IT personnel workstations.

Data Theft Precedes Encryption

The double-extortion ransomware operation involves stealing sensitive information before encrypting systems. The FBI observed Gunra actors collecting business-critical documents, databases, personally identifiable information, and internal email communications. In at least one case, the actors used a malicious executable called main.exe to exfiltrate data from Microsoft OneDrive and SharePoint. Compressed archives containing sensitive information were also transferred to the Mega file-sharing service, with the volume of exfiltrated data reaching tens of terabytes. For encryption, Gunra uses ChaCha20 and RSA-4096 algorithms and has been observed using the .ENCRT extension for encrypted files. A documented sample from July 2025 used the .CRYPT extension. The ransomware also uses Windows Management Instrumentation to delete volume shadow copies before encryption, while one victim had backup and archived data deleted from both primary and disaster recovery infrastructure.

Agencies Urge Patching and Network Segmentation

The authoring agencies recommend that organizations prioritize patching known exploited vulnerabilities in internet-facing systems, including VPN gateways and RDP-exposed infrastructure. They also advise implementing and testing offline, immutable backups stored in physically separate and segmented locations. Network segmentation is another key recommendation, intended to restrict lateral movement and limit the spread of ransomware between systems. The agencies also recommend reviewing domain controllers, servers, workstations and Active Directory environments for unrecognized accounts, auditing administrative privileges, requiring MFA where possible and testing security controls against the Gunra techniques mapped to the MITRE ATT&CK framework. The joint advisory was published August 10, 2026, as part of the ongoing #StopRansomware initiative.