Report
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 | -ep |
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 | rstrtmgr.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 | 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 | 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 Arsinal
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
Phishing-as-a-Service Evolves with Venom
“Whaling” has taken on a new meaning with a highly targeted phishing campaign active from November 2025 through March 2026, aimed exclusively at senior executives from more than 20 industries. The campaign, dubbed VENOM, is a phishing-as-a-service (PhaaS) platform that combines advanced evasion capabilities with immediate persistence of targeted executives. The initial phish impersonates an internal SharePoint document notification and uses embedded QR codes to convince victims to shift to unmanaged mobile devices to bypass corporate security controls. VENOM aims to establish persistence immediately by either registering a new MFA device or retaining long-lived refresh tokens, allowing threat actors to maintain access even after password resets or other base-level remediation efforts.
What’s Notable and Unique
This campaign is unique in its targeted nature of the PhaaS platform rather than broad, sweeping attempts. The threat actors behind VENOM create convincing phishing emails that impersonate SharePoint activity using the victim’s own domain, company name, and even fabricated email threads. These convincing social engineering tactics, combined with the specific targeting of executives, make this an effective capability for cybercriminals.
VENOM operates as a closed-access system, with full adversarial support, but has no public visibility on the dark web or from security researchers. The service likely operates on an invite-only basis, unlike most PhaaS platforms, which typically seek to have as many paying customers as possible. This, among other items such as the sophisticated evasion techniques, indicates a higher degree of sophistication than most other PhaaS offerings.
Either through MFA enrollment or Microsoft Device Code abuse, the threat actor forces the victim to aid them in establishing persistence early in the attack lifecycle. These tactics result in either valid tokens or an additional MFA login method controlled by the threat actor, meaning typical password resets alone are not effective against this technique. Administrators would be required to explicitly revoke sessions and token grants to mitigate the threat actors’ persistence.
Analyst Comments
Oftentimes, MFA is viewed as a one-stop shop to cybersecurity, but tactics such as this show how threat actors can bypass MFA, or worse, use it to establish persistence. Ultimately, this campaign highlights how modern attacks increasingly abuse legitimate authentication workflows rather than attempting to defeat them outright. Defenses that rely solely on MFA without other security posturing, such as continuous session monitoring, token revocation, and identity logging, can leave organizations vulnerable. As attackers shift toward token theft and device trust abuse, incident response and identity security strategies must evolve accordingly.
Sources
Meet VENOM: The PhaaS Platform That Neutralizes MFA
Article
Threat Actors Continue to Leverage BYOVD Technique
Multiple ransomware operations have recently been observed leveraging the Bring Your Own Vulnerable Driver (BYOVD) technique to disable endpoint security controls prior to ransomware deployment. Notably, the Qilin ransomware group commonly leverages a malicious msimg32.dll file loaded via DLL side-loading, along with vulnerable drivers including rwdrv.sys and hlpdrv.sys, to gain kernel-level access and disable security processes. Similarly, Warlock ransomware has been observed exploiting the vulnerable NSecKrnl.sys driver to bypass security controls. The use of BYOVD has also been observed across ransomware campaigns associated with Akira, INC, Medusa, and other threat actors.
What’s Notable and Unique
The Qilin ransomware group employs a sophisticated multi-stage infection chain, leveraging DLL side-loading (msimg32.dll) to execute malicious payloads directly in memory and evade traditional file-based detection. In DLL side-loading, a threat actor tricks a program into loading a malicious dynamic link library. The malware escalates privileges and uses signed but vulnerable drivers (rwdrv.sys and hlpdrv.sys) to bypass security controls, access system memory, and systematically disable endpoint defenses by terminating security processes and disabling monitoring callbacks at the kernel level.
Akira ransomware operators have also exploited the rwdrv.sys and hlpdrv.sys drivers. Additionally, Arete has observed threat actors leveraging multiple other drivers, including the vulnerable TrueSight.sys, to bypass security controls.
Meanwhile, Warlock ransomware operators disguised malicious activity by renaming rclone.exe to TrendSecurity.exe to appear legitimate. The file functioned as a loader, exploiting the vulnerable NSecKrnl.sys driver to disable security processes, while Group Policy Objects (GPOs) were leveraged to systematically disable security controls across the environment.
Analyst Comments
The BYOVD technique, employed by multiple known ransomware operators, reflects a broader shift toward pre-encryption defense evasion, including suppression of Windows telemetry, removal of monitoring callbacks, and abuse of legitimately signed but vulnerable drivers. This technique enables threat actors to evade detection, maintain persistence for extended periods, and maximize the operational impact of ransomware deployment across compromised environments. Organizations should implement strict driver control policies, such as Microsoft’s Vulnerable Driver Blocklist and application control mechanisms. Additionally, enforcing least privilege access, enabling multi-factor authentication (MFA), maintaining up-to-date patching, and continuously monitoring for anomalous driver and kernel-level activity can further reduce the risk of such attacks.
Sources
Qilin EDR killer infection chain
Web Shells, Tunnels, and Ransomware: Dissecting a Warlock Attack
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Ransomware Trends & Data Insights: March 2026
The threat landscape in March had a much more even distribution of threat groups than has been observed since the first half of 2025. Although Akira, Qilin, Play, and INC remained among the most active groups, Arete observed 21 unique ransomware and extortion groups in March, compared to only 15 in February. Akira and Qilin’s activity also declined from the previous month; in February, the two groups were responsible for almost half of all ransomware incidents, but in March they only comprised a little more than a quarter of all activity. Arete also observed activity from several emerging groups in the past month, including BravoX, NightSpire, Payouts King, and Securotrop.
Figure 1. Activity from the top 5 threat groups in March 2026
Analysts at Arete identified several trends behind the threat actors perpetrating cybercrime activities:
In March, threat actors actively exploited FortiGate Next-Generation Firewall appliances as initial access vectors to compromise enterprise networks. The activity involves the exploitation of recently disclosed security vulnerabilities, including CVE-2025-59718, CVE-2025-59719, and CVE-2026-24858, or weak credentials, allowing attackers to gain administrative access, extract configuration files, and obtain service account credentials. Arete also observed Fortinet device exploitation involving various threat groups, with the Qilin ransomware group notably leveraging Fortinet device exploits.
Phishing campaigns leveraging OAuth redirection and a resurgence of Microsoft Teams–based social engineering were also observed in March. In one campaign, attackers sent emails disguised as Microsoft Teams recordings or Microsoft 365 alerts, redirecting victims through legitimate OAuth endpoints to attacker-controlled pages hosting malicious ZIP payloads. A separate campaign has been ongoing since last year, in which attackers flood users’ inboxes with spam and impersonate IT support personnel to trick victims into initiating remote support sessions via tools like Quick Assist.
Arete recently released its 2025 Annual Crimeware Report. Leveraging data and intelligence collected during ransomware and extortion incident response engagements, this report highlights notable trends and shifts in the threat landscape throughout 2025, including Akira’s unusually high activity levels in the second half of 2025, evolving social engineering techniques, and trends in ransom demands and impacted industries.
Sources
Arete Internal
Report
Arete's 2025 Annual Crimeware Report
Harness Arete’s unique data and expertise on extortion and ransomware to inform your response to the evolving threat landscape.