Fortinet FortiOS / FortiProxy authentication bypass (CWE-288), named by joint advisory AA26-222A as a primary Gunra ransomware initial-access vector, abused to create a persistent super-user account on the appliance

Adversaries may obtain and abuse credentials of a default account as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion. Default accounts are those that are built-into an OS, such as the Guest or Administrator accounts on Windows systems. Default accounts also include default factory/provider set accounts on other types of systems, software, or devices, including the root user account in AWS, the root user account in ESXi, and the default service account in Kubernetes.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may obtain and abuse credentials of a domain account as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion. Domain accounts are those managed by Active Directory Domain Services where access and permissions are configured across systems and services that are part of that domain. Domain accounts can cover users, administrators, and services.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may leverage external-facing remote services to initially access and/or persist within a network. Remote services such as VPNs, Citrix, and other access mechanisms allow users to connect to internal enterprise network resources from external locations. There are often remote service gateways that manage connections and credential authentication for these services. Services such as Windows Remote Management and VNC can also be used externally.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network. The weakness in the system can be a software bug, a temporary glitch, or a misconfiguration.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may abuse Windows Management Instrumentation (WMI) to execute malicious commands and payloads. WMI is designed for programmers and is the infrastructure for management data and operations on Windows systems. WMI is an administration feature that provides a uniform environment to access Windows system components.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may abuse the Windows command shell for execution. The Windows command shell (cmd) is the primary command prompt on Windows systems. The Windows command prompt can be used to control almost any aspect of a system, with various permission levels required for different subsets of commands. The command prompt can be invoked remotely via Remote Services such as SSH.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may interact with the native OS application programming interface (API) to execute behaviors. Native APIs provide a controlled means of calling low-level OS services within the kernel, such as those involving hardware/devices, memory, and processes. These native APIs are leveraged by the OS during system boot (when other system components are not yet initialized) as well as carrying out tasks and requests during routine operations.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may obtain and abuse credentials of a default account as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion. Default accounts are those that are built-into an OS, such as the Guest or Administrator accounts on Windows systems. Default accounts also include default factory/provider set accounts on other types of systems, software, or devices, including the root user account in AWS, the root user account in ESXi, and the default service account in Kubernetes.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may obtain and abuse credentials of a domain account as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion. Domain accounts are those managed by Active Directory Domain Services where access and permissions are configured across systems and services that are part of that domain. Domain accounts can cover users, administrators, and services.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may manipulate accounts to maintain and/or elevate access to victim systems. Account manipulation may consist of any action that preserves or modifies adversary access to a compromised account, such as modifying credentials or permission groups. These actions could also include account activity designed to subvert security policies, such as performing iterative password updates to bypass password duration policies and preserve the life of compromised credentials.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may leverage external-facing remote services to initially access and/or persist within a network. Remote services such as VPNs, Citrix, and other access mechanisms allow users to connect to internal enterprise network resources from external locations. There are often remote service gateways that manage connections and credential authentication for these services. Services such as Windows Remote Management and VNC can also be used externally.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may disable or modify multi-factor authentication (MFA) mechanisms to enable persistent access to compromised accounts.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may obtain and abuse credentials of a default account as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion. Default accounts are those that are built-into an OS, such as the Guest or Administrator accounts on Windows systems. Default accounts also include default factory/provider set accounts on other types of systems, software, or devices, including the root user account in AWS, the root user account in ESXi, and the default service account in Kubernetes.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may obtain and abuse credentials of a domain account as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion. Domain accounts are those managed by Active Directory Domain Services where access and permissions are configured across systems and services that are part of that domain. Domain accounts can cover users, administrators, and services.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may manipulate accounts to maintain and/or elevate access to victim systems. Account manipulation may consist of any action that preserves or modifies adversary access to a compromised account, such as modifying credentials or permission groups. These actions could also include account activity designed to subvert security policies, such as performing iterative password updates to bypass password duration policies and preserve the life of compromised credentials.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

In addition to clearing system logs, an adversary may clear the command history of a compromised account to conceal the actions undertaken during an intrusion. Various command interpreters keep track of the commands users type in their terminal so that users can retrace what they've done.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may obtain and abuse credentials of a default account as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion. Default accounts are those that are built-into an OS, such as the Guest or Administrator accounts on Windows systems. Default accounts also include default factory/provider set accounts on other types of systems, software, or devices, including the root user account in AWS, the root user account in ESXi, and the default service account in Kubernetes.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may obtain and abuse credentials of a domain account as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion. Domain accounts are those managed by Active Directory Domain Services where access and permissions are configured across systems and services that are part of that domain. Domain accounts can cover users, administrators, and services.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may employ various means to detect and avoid debuggers. Debuggers are typically used by defenders to trace and/or analyze the execution of potential malware payloads.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may employ various time-based methods to evade detection and analysis. These techniques often exploit system clocks, delays, or timing mechanisms to obscure malicious activity, blend in with benign activity, and avoid scrutiny. Adversaries can perform this behavior within virtualization/sandbox environments or natively on host systems.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may intentionally exclude certain files, folders, directories, file types, or system components from encryption or tampering during a ransomware or malicious payload execution. Some file extensions that adversaries may avoid encrypting include `.dll`, `.exe`, and `.lnk`.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may disable or modify multi-factor authentication (MFA) mechanisms to enable persistent access to compromised accounts.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may disable, degrade, or tamper with security tools or applications (e.g., endpoint detection and response (EDR) tools, intrusion detection systems (IDS), antivirus, logging agents, sensors, etc.) to impair or reduce visibility of defensive capabilities. This may include stopping specific services, killing processes, modifying or deleting tool configuration files and Registry keys, or preventing tools from updating. This may also include impairing defenses more broadly by disrupting preventative, detection, and response mechanisms across host, network, and cloud environments.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may attempt to dump credentials to obtain account login and credential material, normally in the form of a hash or a clear text password. Credentials can be obtained from OS caches, memory, or structures. Credentials can then be used to perform Lateral Movement and access restricted information.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may attempt to access or create a copy of the Active Directory domain database in order to steal credential information, as well as obtain other information about domain members such as devices, users, and access rights. By default, the NTDS file (NTDS.dit) is located in <code>%SystemRoot%\NTDS\Ntds.dit</code> of a domain controller.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may passively sniff network traffic to capture information about an environment, including authentication material passed over the network. Network sniffing refers to using the network interface on a system to monitor or capture information sent over a wired or wireless connection. An adversary may place a network interface into promiscuous mode to passively access data in transit over the network, or use span ports to capture a larger amount of data.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

An adversary may steal web application or service session cookies and use them to gain access to web applications or Internet services as an authenticated user without needing credentials. Web applications and services often use session cookies as an authentication token after a user has authenticated to a website.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may search for common password storage locations to obtain user credentials. Passwords are stored in several places on a system, depending on the operating system or application holding the credentials. There are also specific applications and services that store passwords to make them easier for users to manage and maintain, such as password managers and cloud secrets vaults. Once credentials are obtained, they can be used to perform lateral movement and access restricted information.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may disable or modify multi-factor authentication (MFA) mechanisms to enable persistent access to compromised accounts.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may passively sniff network traffic to capture information about an environment, including authentication material passed over the network. Network sniffing refers to using the network interface on a system to monitor or capture information sent over a wired or wireless connection. An adversary may place a network interface into promiscuous mode to passively access data in transit over the network, or use span ports to capture a larger amount of data.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may attempt to get a listing of network connections to or from the compromised system they are currently accessing or from remote systems by querying for information over the network.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may enumerate files and directories or may search in specific locations of a host or network share for certain information within a file system. Adversaries may use the information from File and Directory Discovery during automated discovery to shape follow-on behaviors, including whether or not the adversary fully infects the target and/or attempts specific actions.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may employ various means to detect and avoid debuggers. Debuggers are typically used by defenders to trace and/or analyze the execution of potential malware payloads.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may use Valid Accounts to log into a computer using the Remote Desktop Protocol (RDP). The adversary may then perform actions as the logged-on user.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may use Valid Accounts to interact with a remote network share using Server Message Block (SMB). The adversary may then perform actions as the logged-on user.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may “pass the hash” using stolen password hashes to move laterally within an environment, bypassing normal system access controls. Pass the hash (PtH) is a method of authenticating as a user without having access to the user's cleartext password. This method bypasses standard authentication steps that require a cleartext password, moving directly into the portion of the authentication that uses the password hash.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may “pass the ticket” using stolen Kerberos tickets to move laterally within an environment, bypassing normal system access controls. Pass the ticket (PtT) is a method of authenticating to a system using Kerberos tickets without having access to an account's password. Kerberos authentication can be used as the first step to lateral movement to a remote system.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may search local system sources, such as file systems, configuration files, local databases, virtual machine files, or process memory, to find files of interest and sensitive data prior to Exfiltration.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may target user email to collect sensitive information. Emails may contain sensitive data, including trade secrets or personal information, that can prove valuable to adversaries. Emails may also contain details of ongoing incident response operations, which may allow adversaries to adjust their techniques in order to maintain persistence or evade defenses. Adversaries can collect or forward email from mail servers or clients.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may access data from cloud storage.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

An adversary may compress and/or encrypt data that is collected prior to exfiltration. Compressing the data can help to obfuscate the collected data and minimize the amount of data sent over the network. Encryption can be used to hide information that is being exfiltrated from detection or make exfiltration less conspicuous upon inspection by a defender.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may transfer tools or other files from an external system into a compromised environment. Tools or files may be copied from an external adversary-controlled system to the victim network through the command and control channel or through alternate protocols such as ftp. Once present, adversaries may also transfer/spread tools between victim devices within a compromised environment (i.e. Lateral Tool Transfer).

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may tunnel network communications to and from a victim system within a separate protocol to avoid detection/network filtering and/or enable access to otherwise unreachable systems. Tunneling involves explicitly encapsulating a protocol within another. This behavior may conceal malicious traffic by blending in with existing traffic and/or provide an outer layer of encryption (similar to a VPN). Tunneling could also enable routing of network packets that would otherwise not reach their intended destination, such as SMB, RDP, or other traffic that would be filtered by network appliances or not routed over the Internet.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may steal data by exfiltrating it over a different protocol than that of the existing command and control channel. The data may also be sent to an alternate network location from the main command and control server.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may use an existing, legitimate external Web service to exfiltrate data rather than their primary command and control channel. Popular Web services acting as an exfiltration mechanism may give a significant amount of cover due to the likelihood that hosts within a network are already communicating with them prior to compromise. Firewall rules may also already exist to permit traffic to these services.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may encrypt data on target systems or on large numbers of systems in a network to interrupt availability to system and network resources. They can attempt to render stored data inaccessible by encrypting files or data on local and remote drives and withholding access to a decryption key. This may be done in order to extract monetary compensation from a victim in exchange for decryption or a decryption key (ransomware) or to render data permanently inaccessible in cases where the key is not saved or transmitted.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may delete or remove built-in data and turn off services designed to aid in the recovery of a corrupted system to prevent recovery. This may deny access to available backups and recovery options.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗

Adversaries may steal monetary resources from targets through extortion, social engineering, technical theft, or other methods aimed at their own financial gain at the expense of the availability of these resources for victims. Financial theft is the ultimate objective of several popular campaign types including extortion by ransomware, business email compromise (BEC) and fraud, "pig butchering," bank hacking, and exploiting cryptocurrency networks.

Evidence: 2026-08-11/gunra-raas-fortios-mfa-backdoor-linux-prng-recoverable · ATT&CK page ↗