A Bad Luck BlackCat

BlackCat (ALPHV) is a Rust-based ransomware-as-a-service operation linked to BlackMatter and REvil lineage, notable for cross-platform samples and a sophisticated exfiltration workflow using Fendr/ExMatter. Telemetry suggests a close tie to past BlackMatter activity through tool reuse, and two notable incidents highlight cloud-resource risk and agile malware reuse across environments.
#ALPHV #BlackCat #BlackMatter #REvil #Fendr #ExMatter

Keypoints

BlackCat/ALPHV is a Rust-written ransomware group operating as a RaaS, targeting multiple corporate victims worldwide.
There is a concrete link to prior BlackMatter/REvil activity via the reuse/modification of the Fendr (ExMatter) exfiltration tool.
Two notable incidents show risk from shared cloud hosting and an agile pattern of malware reuse between BlackMatter and BlackCat.
The malware uses Windows/OS checks, collects machine identifiers (MachineGuid, UUID) for encryption key generation, and employs Windows named pipes for IPC.
It leverages privilege escalation (token impersonation, UAC bypass), credential dumping (Mimikatz, Nirsoft), and lateral movement (compressed PsExec).
Encryption relies on AES/CHACHA20 with BCryptGenRandom, appends a custom extension, and uses hard-coded credentials for propagation and privilege escalation.
Operational maturity is evidenced by expanded file-type exfiltration (Fendr extensions) and broader targeting across industrial environments.

MITRE Techniques

[T1134] Access Token – Token Impersonation – Used for privilege escalation. Quote: ‘Simple process token impersonation.’
[T1548.002] Bypass User Account Control – COM elevation moniker UAC Bypass. Quote: ‘COM elevation moniker UAC Bypass.’
[T1059.003] Windows Command Shell – Malware uses cmd.exe to execute commands. Quote: ‘Using “cmd.exe” malware executes a special command:’
[T1021] Remote Services – Lateral movement with a compressed PsExec tool. Quote: ‘compressed version of PsExec to spread laterally within an organization.’
[T1003.001] Credential Dumping – Mimikatz batch file and Nirsoft utilities used for credentials. Quote: ‘delivered a Mimikatz batch file along with executables and Nirsoft network password recovery utilities.’
[T1490] Inhibit System Recovery – Deletes Shadows via vssadmin to hinder recovery. Quote: ‘vssadmin.exe delete shadows /all /quiet’
[T1082] System Information Discovery – Checks OS version to tailor behavior. Quote: ‘The malware checks which version of the Windows operating system it’s being executed under.’
[T1486] Data Encrypted for Impact – Encrypts files using AES/CHACHA20; key management via BCryptGenRandom. Quote: ‘AES or CHACHA20 algorithms are used for file encryption.’
[T1041] Exfiltration Over C2 Channel – Uses a custom exfiltration tool (Fendr/ExMatter). Quote: ‘modified exfiltration utility that we call Fendr.’
[T1562.001] Impair Defenses – Kills processes and excludes files/folders to aid encryption; also terminates services. Quote: ‘the malware gets a list of services to be killed, as well as files and folders to be excluded from the encryption process, kills processes.’

Indicators of Compromise

[Hash] MD5 – B6B9D449C9416ABF96D21B356A41A28E
[Hash] SHA1 – 38fa2979382615bbee32d1f58295447c33ca4316
[Hash] SHA256 – be8c5d07ab6e39db28c40db20a32f47a97b7ec9f26c9003f9101a154a5a98486
[File name] Sample – <xxx>_alpha_x86_32_windows_encrypt_app.exe
[File size] 2.94 MB
[File extension] .doc, .docx, and other extensions used by Fendr (17146b91dfe7f3760107f8bc35f4fd71)
[Hash] 17146b91dfe7f3760107f8bc35f4fd71 – Fendr extensions set hash