--- analysis: A rule might flag any shell spawned by sqlservr.exe, but this hunt provides the context of external brute-force and specific staging patterns (redirection to ProgramData) to confirm an active intrusion versus an administrator task. blind_spots: - id: no-sql-audit-logs question: Were 'TRUSTWORTHY' or 'clr enabled' parameters changed? requires: Native MS-SQL Audit logs risk: Internal configuration changes in the database engine are invisible to endpoint process monitoring. stage: sql-server-exploitation - id: in-memory-assembly question: Was a malicious DLL loaded into the SQL process memory? requires: hb_module_activity with CLR monitoring risk: The SqlShell malware may run as a reflectively loaded assembly, bypassing file-on-disk and process-launch detection. stage: sql-server-exploitation coverage: - stage: sql-brute-force-access status: covered steps: - mssql-brute-force - stage: sql-server-exploitation status: covered steps: - sqlservr-child-processes - stage: initial-payload-delivery status: covered steps: - scripted-payload-staging - reason: Belongs to another part of the 'Mallox ransomware affiliate leverages PureCrypter in MSSQL exploitation' series. stage: loader-evasion-and-anti-analysis status: out_of_scope - reason: Belongs to another part of the 'Mallox ransomware affiliate leverages PureCrypter in MSSQL exploitation' series. stage: persistence-run-key status: out_of_scope - reason: Belongs to another part of the 'Mallox ransomware affiliate leverages PureCrypter in MSSQL exploitation' series. stage: mallox-ransomware-execution status: out_of_scope guardrails: claims: no_unsupported evidence: citation_required missing_data: not_benign telemetry: untrusted hunt: applicability: campaign-specific handoff: promote-to-detection justification: MS-SQL servers are frequent targets for high-impact ransomware. Brute-force and exploitation of administrative features (xp_cmdshell) are durable TTPs used by Mallox affiliates to achieve initial access. methodology: model-assisted trigger: intel-report hypothesis: An adversary is targeting MS-SQL servers via brute-force of the sa account to execute administrative commands that stage payloads in public directories. labels: - hunt - attack.t1110 - attack.t1190 - attack.t1059.003 - attack.t1059.001 - attack.t1047 name: Mallox MS-SQL Exploitation and Initial Delivery parameters: lookback_days: default: '14' description: Days of history to examine. from: kind: manual observed: '2024-05-02' ref: hunt-standard type: number sa_account: default: sa description: The SQL administrator account name to monitor for brute-force. from: kind: article observed: '2024-05-02' ref: https://blog.sekoia.io/mallox-ransomware-affiliate-leverages-purecrypter-in-microsoft-sql-exploitation-campaigns/ type: string scope_hosts: default: [] description: Limit the hunt to these hostnames; leave empty to hunt across the entire estate. from: kind: manual observed: '2024-05-02' ref: hunt-standard type: list[host] suspicious_sql_child_procs: default: - cmd.exe - powershell.exe - wmic.exe - scrcons.exe description: Process names spawned by sqlservr.exe that suggest feature abuse. from: kind: article observed: '2024-05-02' ref: https://blog.sekoia.io/mallox-ransomware-affiliate-leverages-purecrypter-in-microsoft-sql-exploitation-campaigns/ type: list[string] provenance: authors: - name: Huntbase hunt generation org: huntbase.io generated: by: huntbase-hunt-generation from: https://blog.sekoia.io/mallox-ransomware-affiliate-leverages-purecrypter-in-microsoft-sql-exploitation-campaigns/ gates: - dry-run - lint - critic model: hb_google/gemini-3-flash-preview rationale: Focus on servers identified as running Microsoft SQL Server. If the estate is large, prioritize those with external exposure. references: - name: "Sekoia \u2014 Mallox ransomware affiliate leverages PureCrypter in MSSQL\ \ exploitation" url: https://blog.sekoia.io/mallox-ransomware-affiliate-leverages-purecrypter-in-microsoft-sql-exploitation-campaigns/ related: - hunt: purecrypter-loader-evasion reason: The next phase of this attack involves PureCrypter's anti-analysis and loader behavior. relation: follows - hunt: mallox-impact-and-encryption reason: A sibling hunt focusing on the final encryption and shadow copy deletion phases. relation: sibling scenario: stages: - name: MS-SQL Brute Force observables: - Brute-force attempts against 'sa' account - Source IP address in AS208091 (XHost Internet Solution) - Approximately 320 authentication attempts per minute - Targeting MS-SQL port (1433) slug: sql-brute-force-access tactic: initial-access techniques: - T1110 - T1190 - name: MS-SQL Feature Exploitation observables: - Enabling 'TRUSTWORTHY' database parameter - Enabling 'clr enabled' parameter - Creating assembly named 'shell' (SqlShell DLL) - Creating stored procedure 'cmd_exec' - Enabling 'xp_cmdshell' configuration - Enabling 'Ole Automation Procedures' - Use of 'sp_oacreate' to create 'wscript.shell' OLE object - Application name 'vYMiFrYR' in SQL connection logs slug: sql-server-exploitation tactic: execution techniques: - T1059.003 - name: PowerShell Downloader and WMIC Execution observables: - echo and redirect used to create PowerShell script - PowerShell script saved to C:\ProgramData - WMIC used to execute downloaded binary - Downloading multimedia-themed files (e.g., .mp4, .wav, .pdf) containing encrypted payloads slug: initial-payload-delivery tactic: execution techniques: - T1059.001 - T1047 - name: PureCrypter Anti-Analysis and Evasion observables: - WMI query 'select * from Win32_BIOS' to check for VMWare, Virtual, AMI, or Xen - WMI query 'select * from Win32_ComputerSystem' to check for Microsoft or VMWare - Process search for 'SbieDll.dll' - Monitor size check for 1440x900 - Username check for 'john', 'anna', or 'xxxxxxxx' - Execution of 'ipconfig /renew' and 'ipconfig /release' for network testing - Patching 'EtwEventWrite' and 'AmsiScanBuffer' in memory - Adding Windows Defender exclusions via 'MpPreference -Exclusion' slug: loader-evasion-and-anti-analysis tactic: defense-evasion techniques: - T1497.001 - T1562.001 - T1129 - name: Registry Run Key Persistence observables: - Registry key addition in 'Software\Microsoft\Windows\CurrentVersion\Run\' slug: persistence-run-key tactic: persistence techniques: - T1547.001 - name: Mallox Ransomware Execution observables: - Ransomware executable named 'Ydxhjxwf.exe' in %appdata% - Reflective code loading of stage 2 DLL - Elevation of process privileges with 'SeDebugPrivilege' slug: mallox-ransomware-execution tactic: impact techniques: - T1486 summary: An affiliate of Mallox ransomware targets internet-facing MS-SQL servers using brute-force attacks against the 'sa' account. Upon gaining access, the attacker exploits SQL features such as CLR assemblies and xp_cmdshell to deliver PureCrypter, a .NET loader that employs extensive anti-analysis and evasion techniques before executing the final Mallox ransomware payload. series: index: 1 slug: mallox-ransomware-affiliate-leverages-purecrypter-in-mssql-exploitation title: Mallox ransomware affiliate leverages PureCrypter in MSSQL exploitation total: 2 severity: high targets: analyst: name: Tier-2 analyst role: analyst endpoint: category: endpoint name: Endpoint telemetry (hb_ surfaces) telemetry: - endpoint hunter: agent: true name: Hunt agent identity: category: identity name: Identity / sign-in telemetry telemetry: - identity tlp: clear type: investigation --- # Mallox MS-SQL Exploitation and Initial Delivery This hunt identifies the early stages of a Mallox ransomware intrusion by monitoring the intersection of authentication failure volume, database engine process anomalies, and shell-based payload staging. It specifically targets the exploitation of MS-SQL features like xp_cmdshell or OLE automation used to drop and execute PureCrypter or Mallox loaders. ## sql-server-inventory Scope the hunt to hosts known to run MS-SQL packages. ```sqlite target=endpoint role=scoping ~~~yaml expected: A list of hostnames. Silence indicates no SQL servers are inventoried. reads: - device_hostname - package_name - vendor_name silence: not_evidence_of_absence source: hb_software_inventory verified: dry-run verified_at: '2026-09-17' ~~~ SELECT DISTINCT device_hostname FROM hb_software_inventory WHERE (LOWER(package_name) LIKE '%sql server%' OR LOWER(vendor_name) LIKE '%microsoft%sql%') ``` ## parallel-triage parallel: - → mssql-brute-force - → sqlservr-child-processes - → scripted-payload-staging join: → triage-exploitation ## mssql-brute-force Detect high-frequency login failures on the SQL admin account. ```sqlite target=identity role=baseline params=(lookback_days=lookback_days, sa_account=sa_account, scope_hosts=scope_hosts) ~~~yaml baseline: compare: new_this_window window: '{{lookback_days}}d' expected: One or more source IPs with hundreds of failures. Silence means no sa-targeted brute-force detected. prevalence: by: dst_endpoint_name key: - src_endpoint_ip rare_below: 5 reads: - src_endpoint_ip - dst_endpoint_name - actor_user_name - activity_id - time silence: not_evidence_of_absence source: hb_auth_signin verified: dry-run verified_at: '2026-09-17' ~~~ SELECT src_endpoint_ip, dst_endpoint_name, COUNT(*) as attempt_count, MIN(time) as first_seen, MAX(time) as last_seen FROM hb_auth_signin WHERE LOWER(actor_user_name) = '{{sa_account}}' AND activity_id = 5 AND time >= datetime('now', '-{{lookback_days}} days') AND ('{{scope_hosts}}' = '' OR instr(',' || '{{scope_hosts}}' || ',', ',' || dst_endpoint_name || ',') > 0) GROUP BY src_endpoint_ip, dst_endpoint_name HAVING attempt_count > 100 ORDER BY attempt_count DESC ``` ## sqlservr-child-processes Detect instances of sqlservr.exe spawning shells or WMIC, indicative of xp_cmdshell abuse. ```sqlite target=endpoint role=detection-candidate params=(lookback_days=lookback_days, scope_hosts=scope_hosts, suspicious_sql_child_procs=suspicious_sql_child_procs) ~~~yaml expected: Rows showing the SQL engine spawning cmd.exe or powershell.exe. Silence proves no such shells were captured by process logging. reads: - device_hostname - process_name - process_cmd_line - parent_process_name - time silence: evidence_of_absence source: hb_process_activity verified: dry-run verified_at: '2026-09-17' ~~~ SELECT device_hostname, process_name, process_cmd_line, parent_process_name, time FROM hb_process_activity WHERE LOWER(parent_process_name) LIKE '%sqlservr.exe' AND instr(',' || '{{suspicious_sql_child_procs}}' || ',', ',' || LOWER(process_name) || ',') > 0 AND time >= datetime('now', '-{{lookback_days}} days') AND ('{{scope_hosts}}' = '' OR instr(',' || '{{scope_hosts}}' || ',', ',' || device_hostname || ',') > 0) ``` ## scripted-payload-staging Find script blocks writing to ProgramData using shell redirection, as seen in Mallox affiliate scripts. ```sqlite target=endpoint role=triage params=(lookback_days=lookback_days, scope_hosts=scope_hosts) ~~~yaml expected: Script content showing binary creation or downloader staging. Silence suggests this specific affiliate tradecraft is absent. reads: - device_hostname - script_path - script_content - time silence: not_evidence_of_absence source: hb_script_activity verified: dry-run verified_at: '2026-09-17' ~~~ SELECT device_hostname, script_path, script_content, time FROM hb_script_activity WHERE (LOWER(script_content) LIKE '%echo%' AND (LOWER(script_content) LIKE '%>%' OR LOWER(script_content) LIKE '%>>%') AND LOWER(script_content) LIKE '%\programdata\%') AND time >= datetime('now', '-{{lookback_days}} days') AND ('{{scope_hosts}}' = '' OR instr(',' || '{{scope_hosts}}' || ',', ',' || device_hostname || ',') > 0) ``` ## triage-exploitation ```agent target=hunter cite: required context: - mssql-brute-force - sqlservr-child-processes - scripted-payload-staging max_iterations: 4 objective: Decide if the brute-force and subsequent SQL processes indicate a successful MS-SQL compromise. success_criteria: A verdict of malicious | suspicious for any host with brute-force followed by shell execution. tools: - endpoint - identity ``` ## route-verdict if~: "the triage verdict is malicious for at least one host, specifically showing shell execution originating from sqlservr.exe" (confidence: high, judge=hunter) then: → isolate-host indeterminate: → analyst-review unavailable: → analyst-review (blind_spot: no-sql-audit-logs) else: → close-out ## isolate-host ```action target=endpoint ~~~yaml approval: required ~~~ Isolate the compromised host and rotate the 'sa' account password. ``` → analyst-review ## analyst-review ```manual target=analyst Review internal SQL tables for 'shell' assembly and 'cmd_exec' stored procedure. Check C:\ProgramData for scripts or multimedia-extension files (.mp4, .wav). ``` → end ## close-out ```manual target=analyst Document absence of SQL exploitation and recommend implementing account lockout policies for the sa account. ``` → end