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Threat Actor Spotlight: BlackSuit Ransomware

Arete Analysis

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Executive Summary

Since May 2023, Arete’s Incident Response (IR) team has responded to multiple BlackSuit ransomware engagements against organizations in the healthcare, financial services, manufacturing, professional services, public service, entertainment, and retail sectors. This spotlight explores the ransomware behavior observed, statistics from IR engagements, and background information on the threat actor. Finally, we discuss security recommendations to better defend against this evolving cyber threat and mitigate the risk of financial and reputational losses arising from these incidents.

Incident Response Data on BlackSuit Ransomware

The information below is based on BlackSuit incidents investigated by Arete since May 2023. Our IR and teams work together to analyze key data points during every ransomware engagement and form real-time threat actor (TA) insights.

  • Arete has investigated dozens of engagements involving BlackSuit.

  • We have been extremely successful in negotiating discounted ransoms with this TA.

  • The highest observed ransom demand is around $18 million.

  • The average initial demand is around $2.5 million.

  • The average ransom payment facilitated is around $500,000.

  • Commonly observed methods of intrusions include remote desktop protocol (RDP), virtual private network (VPN), and firewall vulnerabilities.

  • Tools observed during the investigations include CobaltStrike, WinRAR, PUTTY, Rclone, Advanced IP Scanner, Network Scanner, Mimikatz, and GMER.

  • A commonly observed ransom note filename is readme.blacksuit.txt.

  • In some instances, backups were encrypted or deleted, while in others, backups were used for restoration.

Background

The information about the BlackSuit threat actor group in this section was shared in Arete’s 2024 Q1 Crimeware Report.

The most notable newcomer in Q1 was BlackSuit, the third most active group of Q1. Although Arete first observed BlackSuit ransomware operating in May 2023, it only accounted for less than a half percent of the total engagements in 2023. The group significantly increased its activity in Q1 2024, and there were more BlackSuit engagements in February 2024 alone than in all of 2023. BlackSuit operates as a private group without affiliates, targeting both Windows and Linux users and utilizing a double extortion method of stealing and encrypting sensitive data on a victim’s network.

BlackSuit: A Continuation of Royal Ransomware?

The BlackSuit ransomware payload has significant code overlap with Royal ransomware, and the Cybersecurity and Infrastructure Security Agency (CISA) and the FBI believe BlackSuit to likely be a rebranding or spinoff variant of Royal. While BlackSuit could be using the same developer or code with slight modifications, Arete also observed language used by BlackSuit in ransom negotiations identical to previous engagements with Royal, which lends to the assessment that the group might be a rebrand or offshoot. Regardless, BlackSuit’s emergence demonstrates that although names may change, threat actors will find ways to adapt and evolve their operations.

Figure 1. Language from two separate BlackSuit TOR chats (Source: Arete)

Figure 2. Identical language from two separate Royal TOR chats (Source: Arete)

Technical Analysis

Malware analysis revealed that BlackSuit ransomware:

  • Supports multiple command-line arguments.

  • Encrypts files on the system and mounted shares.

  • Adds the following extension to encrypted files: .blacksuit (e.g., file.docx.blacksuit).

  • Creates a ransom note with the following filename: readme.blacksuit.txt.

  • Self-identifies the group as BlackSuit in the ransom note.

  • References a data leak site in the ransom note that, when accessed, self-identifies the group as BlackSuit.

  • Kills a list of processes and services.

  • Maintains a list of whitelisted files and directories to make sure it will not render the system unusable, preventing recovery when running a decryptor.

  • Attempts to prevent system recovery by deleting the system’s volume shadow copies.

  • Creates the following mutex during execution: WLm87eV1oNRx6P3E4Cy9.

Execution Pattern/Arguments

BlackSuit ransomware needs command line arguments to execute and encrypt files in the system. Command line arguments supported:

Command line argument
Description

-id [32-byte characters]

Ransomware ID

-size

Invoked with drag and drop

-ep

Number that represents the percentage of the file that will be encrypted

-path [target_directory_path]

Used to specify a target directory to encrypt

-localonly

Encrypt only the local system

-networkonly

Encrypt only shared volumes/directory

-aavm

Encrypt all files

The ransomware will not execute in the system without the “–id” argument followed by a 32-character value that is unique in each engagement and present in the ransom note TOR URL. Portion of the data in the ransom note that contains the ID:

All your files will be decrypted, your data will be reset, your systems will stay in safe. Contact us through TOR browser using the link:

http://c7jpc6h2ccrdwmhofuij7kz6sr2fg2ndtbvvqy4fse23cf7m2e5hvqid[.]onion/?id=[32-characters]

Execution of ransomware to encrypt files:

blacksuit.exe -id [32-characters]

The ransomware developer coded the logic to allow configuration of the 32-character value in the command line during execution. This same victim-specific 32-character string value is then added to the ransom note URL used for negotiations. Due to this implementation in the ransomware code, threat researchers can execute the ransomware without knowing the 32-character string value, as any value of this type can be used to execute the malicious code. In analyzing Royal ransomware samples, Arete found a similarity in that any 32-character value can be supplied to execute the ransomware, and the value is also added to the ransom note TOR chat URL.

Example of how the ransom note content looks with a randomly supplied string (e.g., blacksuit.exe -id 7777777777777777777777777777777):

All your files will be decrypted, your data will be reset, your systems will stay in safe. Contact us through TOR browser using the link:

http://c7jpc6h2ccrdwmhofuij7kz6sr2fg2ndtbvvqy4fse23cf7m2e5hvqid[.]onion/?id=77777777777777777777777777777777777777


Obfuscated Files or Information: Software Packing

Most of the strings in the ransomware are encoded. The encoded strings are hardcoded and decoded at runtime. Every encoded string has its own decoding loop:

Figure 3. Encoded strings hardcoded

Figure 4. String decoding loop


Some relevant strings decoded in memory:

Global\\\WLm87eV1oNRx6P3E4Cy9
readme.blacksuit.txt
\windows\
svchost.exe
explorer.exe
-size
cmd.exe /c vssadmin delete shadows /all /quiet

-ep
-path
-localonly
-networkonly
-aavm
Microsoft Enhanced RSA and AES Cryptographic Provider


Obfuscated Files or Information: Dynamic API Resolution

To avoid static or other defensive analysis, the ransomware uses dynamic API resolution to conceal malware characteristics and functionality. The ransomware initially decrypts DLL names, then loads the APIs. Hardcoded encoded DLL names are shown below:

Figure 5. Encoded DLL names

Figure 6. DLL name decoding loop

DLL names decoded at runtime:

shell32.dll
user32.dll
advapi32.dll
ws2_32.dll
shlwapi.dll

rstrtmgr.dll
ntdll.dll
Crypt32.dll
iphlpapi.dll


Stop Services and Processes

Before file encryption, the ransomware terminates a list of known running processes and services to encrypt as many files as possible. BlackSuit ransomware utilizes the Windows Restart Manager to terminate any process using files other than explorer.exe or a critical process.

Sequence of Windows Restart Manager APIs used by the ransomware:

RmStartSession

Starts the Restart Manager session.

RmRegisterResources

Registers resources, in this case the targeted filename

RmGetList

Determine which processes or services are using the registered resource (file)

RmShutdown

Shuts down any identified process or service using the registered resource

RmEndSession

Closes the Restart Manager session.

The ransomware also uses Windows native CreateToolhelp32Snapshot, Process32FirstW, and Process32NextW APIs to enumerate processes in the system.


File and Directory Exclusions

The ransomware excludes system-related files and folders, ransomware-related files, and whitelisted extensions during encryption.

Excluded file extensions:

.com .ani .scr .drv .hta .rom .bin .msc .ps1 .shs .adv .msu .prf .bat .idx .mpa .cmd .msi .mod .ocx .ics .386 .sys .rtp .wpx .msp .cab .ldf .lnk .cur .nls .hlp .key .ico .exe .icns .lock .theme .diagpkg .diagcab .nomedia .diagcfg .msstyles .themepack .blacksuit .deskthemepack

Excluded files and directories:

“msocache”, “intel”, “$recycle.bin”, “windows”, “windows.old”, “mozilla firefox”, “$WinREAgent”, “boot”, “google”, “perflogs”, “system volume information”, “appdata”, “tor browser”, “$windows.~ws”, “application data”, “$windows.~bt”, “mozilla”, “readme.blacksuit.txt”


Inhibit System Recovery

Windows operating systems contain features that can help fix corrupted system files, including shadow copies, which are backups of files created by the Volume Shadow Copy Service (VSS). By deleting shadow copies, the ransomware can prevent victims from restoring files from backups, making it more difficult for them to recover their data without paying the ransom.

With the CreateProcessW function, the ransomware deletes volume shadow copies before file encryption by executing the following command:

cmd.exe /c vssadmin delete shadows /all /quiet

Code in the ransomware showing this operation (the EAX register contains the kernel32.CreateProcessW address):

Figure 7. Create process call to delete volume shadow copies


System Network Connections Discovery

BlackSuit ransomware can enumerate network-mounted shares by scanning the network interfaces.

Data Encrypted for Impact

The ransomware initially finds available drives and loads the files one by one using the Windows API FindFirstFileW and FindNextFileW. It then uses OpenSSL AES keys to encrypt the files and adds the extension .blacksuit to the encrypted file name.

Figure 8. Windows native CryptEncrypt API call to encrypt the data


Public key:

—–BEGIN RSA PUBLIC KEY—–

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

—–END RSA PUBLIC KEY—–

The ransomware encrypts files, adds the .blacksuit extension at the end of the encrypted files, and adds the following bytes at the end of the file (“??” represents variable bytes):

00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ?? 00 00 00 ??

00 00 00

Figure 9. “.blacksuit” extension added to the encrypted files

Figure 10. Padding bytes in encrypted files


Upon successful execution, the ransomware creates ransom notes with the file name readme.blacksuit.txt.

Figure 11. Screenshot of BlackSuit ransom note


Modify Registry

The ransomware did not perform any registry key modification.

Mutex

The mutex is the fundamental tool for managing shared resources between multiple threads or processes. Typically, ransomware uses a mutex to avoid reinfecting the victim system and causing multiple layers of encryption. The ransomware creates the following mutex value: “WLm87eV1oNRx6P3E4Cy9”.

Figure 12. Screenshot of the mutex value created while debugging the ransomware


Network Activity

The ransomware did not try to communicate with a remote server other than encrypting data from mounted shares.

Indicators of Compromise

Indicator
Type
Context

f1684fb118d4d8fc56653fcc49e12a659b64c4459ba037fa94f21783235cc6ba
dede96fd44c0f78eb79ceb63b898874e8922efc59d8bfb9f86505b1992bc00a3
79ab73a0e9dd8eac045c00fd1bd172a7f359588901f93c83e6740157eb21e7df
d96ff4b3e188f7ff96ed28c1381a6318dd76bb1fbd6ca02c6ab0236e1c7f35aa

SHA256 hash

BlackSuit ransomware

C:\readme.blacksuit.txt

File path

BlackSuit ransom note

.blacksuit

Extension

Encrypted files extension

vssadmin delete shadows /all /quiet

Process

Volume Shadow Copy deletion

WLm87eV1oNRx6P3E4Cy9

Mutex

Mutex value object created by the BlackSuit ransomware

Any 32-character string

Password

Command line argument needed to properly execute the ransomware. The ransomware developer doesn’t validate it

c7jpc6h2ccrdwmhofuij7kz6sr2fg2ndtbvvqy4fse23cf7m2e5hvqid [.]onion
weg7sdx54bevnvulapqu6bpzwztryeflq3s23tegbmnhkbpqz637f2yd[.]onion

URL

TA data leak site (DLS)


Data Leak Site

The ransom note contains a data leak site (DLS) that displayed the following page, self-identifying the group as BlackSuit:

Figure 13. TOR DLS: c7jpc6h2ccrdwmhofuij7kz6sr2fg2ndtbvvqy4fse23cf7m2e5hvqid[.]onion

Figure 14. TOR DLS: weg7sdx54bevnvulapqu6bpzwztryeflq3s23tegbmnhkbpqz637f2yd[.]onion


Detection Mechanisms

Custom Detections and Blocking with Arete’s Arete Bloktd℠


Yara


Recommended Mitigations

  • Utilize an endpoint detection and response (EDR) solution with the capability to halt detected processes and isolate systems on the network based on identified conditions.

  • Block any known attacker C2s in the firewall.

  • Implement multi-factor authentication on RDP and VPN to restrict access to critical network resources.

  • Eliminate unnecessary RDP ports exposed to the internet.

  • Block a high number of SMB connection attempts from one system to others in the network over a short period of time.

  • Perform periodic dark web monitoring to verify if data is available for sale on the black market.

  • Perform penetration tests.

  • Periodically patch systems and update tools.

  • Monitor connections to the network from suspicious locations.

  • Monitor downloads and uploads of files to file-sharing services outside standard work hours.

  • Monitor file uploads from domain controllers to the internet.

  • Monitor network scans from uncommon servers (e.g., RDP server).

Organizations can find the full list of US government recommended ransomware prevention and mitigation guidance here: https://www.cisa.gov/stopransomware/ransomware-guide.

Arete provides data-driven cybersecurity solutions to transform your response to emerging cyber threats. Learn more.


References

Back to Blog Posts

Article

FortiBleed Campaign Linked to INC and Lynx Ransomware Operations

Researchers have linked the FortiBleed credential-harvesting campaign to the INC and Lynx ransomware-as-a-service (RaaS) operations, establishing a direct connection between large-scale FortiGate credential theft and subsequent ransomware deployment. The attribution is based on a variety of factors, including an operator observed managing negotiation panels for both ransomware groups, notable overlap between FortiBleed victim data and subsequent ransomware targets, and internal infrastructure exposing attack workflows. The campaign is estimated to have targeted more than 430,000 internet-facing FortiGate devices, resulting in administrative access to hundreds of organizations. 

What’s Notable and Unique

  • Researchers identified a shared operator actively managing negotiation panels for both the INC and Lynx ransomware groups, providing rare operational evidence linking the two RaaS operations beyond infrastructure or malware similarities. 


  • Analysis of the exposed infrastructure revealed a structured ransomware operation with dedicated roles for access acquisition, victim management, negotiations, and technical support, reflecting an organized ransomware-as-a-service (RaaS) model rather than an ad hoc criminal group. 


  • The operation reportedly integrates artificial intelligence into multiple stages of the attack lifecycle, including vulnerability research, penetration testing, attack automation, and ransomware development, demonstrating the increasing adoption of AI to enhance offensive capabilities.

Mitigations

Organizations should assume that exposed or previously compromised FortiGate credentials may be leveraged for ransomware deployment and immediately reset administrative and VPN credentials while enforcing multi-factor authentication (MFA) for all privileged access. Security teams should ensure that FortiGate appliances are fully patched, restrict management interfaces to trusted networks, and audit administrative accounts and firewall configurations for unauthorized changes. Organizations should also monitor for anomalous authentication activity, hunt for published indicators of compromise (IOCs), and review VPN and firewall logs for signs of unauthorized access. Maintaining centralized logging and a well-practiced incident response process can help detect and contain attacks before they progress to lateral movement or ransomware deployment.

Analyst Comments

The attribution of FortiBleed to the INC and Lynx ransomware operations reinforces the growing convergence between credential-harvesting campaigns and ransomware deployment, highlighting the role of initial access operations in modern RaaS ecosystems. The relationship between INC and Lynx also aligns with Arete's previous research, which identified a shared malware lineage. INC Ransom, first observed in 2023, was later leaked or sold, enabling code reuse by other threat actors. Lynx, which emerged in 2024, is widely regarded as an evolution of the INC codebase. Sinobi ransomware, identified in 2025, shares near-identical binaries and infrastructure, and approximately 99% code similarity with Lynx. Further details on the code correlation between INC, Lynx, and Sinobi are available in Arete's 2025 Annual Report.

Sources

  • Is FortiBleed Linked to INC and Lynx Ransomware?   

  • FortiBleed credential-theft campaign linked to Lynx ransomware   

  • FortiBleed Unmasked: A Joint Operation by Lynx and INC Ransomware Groups   

  • FortiBleed Credential Theft Campaign Attributed to INC and Lynx Ransomware Groups  

Article

Ransomware Trends & Data Insights: June 2026

Although Akira was once again the most active ransomware threat in June, activity remained relatively distributed among multiple threat groups, with 17 unique threat groups observed throughout the month. Along with Akira, Qilin and INC Ransom remained active and were among the top five most active threat groups observed in June. Several new threat actors also emerged during the month, including KryBit, Settra, and Icarus.

Figure 1. Activity from the top 5 threat groups in June 2026

Throughout the month, analysts at Arete identified several trends behind the threat actors perpetrating cybercrime activities:

  • In June, a threat actor calling themselves Icarus compromised and exfiltrated data from customers of the market intelligence platform Klue. Klue later confirmed the security incident, which involved attackers stealing OAuth tokens used to connect to customers' Salesforce environments, and reported that the threat actor was deleting the data stolen from affected Klue customers. In an odd twist, reports emerged of a second threat actor claiming to have compromised Icarus's infrastructure and attempting to re-extort Klue's customers. Regardless, the Klue breach highlights the growing threat of software-as-a-service (SaaS) supply chain compromises, particularly those exploiting OAuth tokens and trusted integrations to bypass traditional security controls.

  • In mid-June, security researchers identified a large-scale credential-harvesting and valid account abuse campaign dubbed “FortiBleed” that systematically targets internet-facing Fortinet FortiGate firewalls and SSL-VPN gateways, relying heavily on automated password spraying and configuration exfiltration rather than vulnerability exploitation. The scale of exposure and attack activity has been significant and globally distributed, with attackers collecting the login credentials of over 86,000 FortiGate devices across 194 countries. There is no singular ‘fix’ to mitigate the database exposure, and it is important that organizations work with their security teams, incident response providers, and other stakeholders to review environments holistically and monitor for signs of potentially unauthorized activity.

  • Multiple threat groups continue to leverage vulnerable drivers to bypass endpoint detection and response (EDR) solutions in a technique known as Bring Your Own Vulnerable Driver (BYOVD). Arete has observed Akira and DragonForce using the technique in multiple engagements, and The Gentlemen ransomware-as-a-service (RaaS) has also been observed using what researchers are calling "GentleKiller", a framework consisting of multiple variants that leverage vulnerable drivers and EDR-disabling utilities to target a wide range of endpoint security products.  

Sources

  • Arete Internal

Article

Update on FortiBleed Credential Exposure

Last week, security researchers identified a large-scale credential-harvesting and valid account abuse campaign dubbed “FortiBleed” that systematically targets internet-facing Fortinet FortiGate firewalls and SSL-VPN gateways. The campaign relies heavily on automated password spraying and configuration exfiltration rather than vulnerability exploitation.

  • Attackers first scan for exposed FortiGate devices and rank targets based on revenue. SSH brute-force attacks are used against admin accounts to gain initial access.

  • Following initial access, operators deploy stealthy packet-sniffing capabilities and establish external listening posts to receive harvested credentials and session data in near real time.

  • Observed post-exploitation activity strongly indicates pre-positioning for broader enterprise compromise, including lateral movement and potential ransomware deployment.

  • The scale of exposure and attack activity has been significant and globally distributed. The campaign has been ongoing since at least February 2026, with attackers collecting the login credentials of over 86,000 FortiGate devices across 194 nations.

How Arete Can Help

Arete continues to monitor this campaign, utilizing our extensive experience in detection, threat hunting, and attack surface review to look for indications of unauthorized activity related to this database exposure. Additional information regarding important considerations, containment and credential compromise mitigation actions, and additional hardening recommendations can be found in Arete’s FortiBleed Advisory.

Sources

  • FortiBleed: SOCRadar’s Investigation into 86,644 Compromised Fortinet Firewalls

  • FortiBleed Attackers Turn Firewalls Into Credential Stealers as Heists Persist

  • FortiBleed: The Most Detailed Breakdown Yet of an Active Russian Credential-Harvesting Operation

  • Hackers Using FortigateSniffer Tool That Turns Compromised Firewalls Into Password Collectors  

Article

Europol Disrupts AudiA6 Crypto Laundering Service

European authorities have dismantled AudiA6, a major cryptocurrency laundering service linked to ransomware groups and broader cybercriminal networks. Between 2022 and 2025, the platform is believed to have processed over €336 million in illicit funds, enabling threat actors to obscure financial trails and monetize cybercrime proceeds. Its operators are also suspected of running Dark2Web, a dark web forum that facilitated collaboration, services, and connections among cybercriminals globally. This development underscores the expanding role of sophisticated, large-scale cryptocurrency laundering services in sustaining the cybercrime economy, enabling threat actors to obscure illicit funds and evade regulatory controls.

What’s Notable and Unique 

  • Following law enforcement disruption of Cryptex and Garantex, AudiA6 emerged as another platform involved in financial activities linked to ransomware groups. Investigators believe that AudiA6 became a central hub for cybercriminals seeking to launder stolen digital assets while obscuring the transaction trail from authorities.

  • On June 10, 2026, a coordinated operation resulted in two arrests in Georgia, the dismantling of key infrastructure (30+ servers, 25 domains), the freezing or seizure of over €778,000 in crypto, and the takedown of the AudiA6 and Dark2Web platforms. 

Analyst Comments

Ransomware groups and cybercriminal networks are increasingly leveraging sophisticated techniques, including chain-hopping, decentralized exchanges, and mixer-as-a-service platforms, to rapidly move illicit cryptocurrency across multiple blockchains, effectively obscuring transaction trails. Concurrently, the widespread use of fraudulent exchange accounts, mule wallets, and privacy-enhancing tools has elevated cryptocurrency laundering to a core enabler of the cybercrime ecosystem, allowing actors to bypass anti-money-laundering controls at scale. This investigation identified over 6,000 KYC records linked to money-mule accounts, many of which were tied to Russian-speaking intermediaries specifically recruited to facilitate the movement of illicit proceeds. These threat actors systematically used both commercial and domain-controlled email services to establish mule accounts across multiple cryptocurrency platforms. Collectively, these findings underscore the growing scale, coordination, and professionalization of cryptocurrency-enabled crime, highlighting the critical need for sustained, intelligence-led, and internationally coordinated efforts to disrupt these evolving financial ecosystems.

Sources

  • Ransomware gangs cut off from EUR 336 million ‘AudiA6’ crypto laundering pipeline