Detection Rules and Hunting Queries

full_test_enc.exe (Arsenal-237 Rust Ransomware)

---

YARA Rules

Rule 1: Exact Hash Detection (Highest Confidence)

rule Arsenal237_FullTestEnc_ExactHash {
    meta:
        description = "Detects full_test_enc.exe by exact cryptographic hash"
        author = "Threat Intelligence Team"
        date = "2026-01-27"
        malware_type = "Ransomware"
        threat_level = "CRITICAL"
        confidence = "DEFINITE"
        reference = "Arsenal-237 Toolkit"

    strings:
        // File hashes
        $sha256 = { 4d 1f e7 b5 4a 0c e9 ce 20 82 c1 67 b6 62 ec 13 8b 89 0e 3f 30 5e 67 bd c1 3a 5e 9a 24 70 85 18 }
        // Note: YARA hex patterns are for demonstration; use native hash matching in YARA 4.2+

    hashes:
        sha256 = "4d1fe7b54a0ce9ce2082c167b662ec138b890e3f305e67bdc13a5e9a24708518"
        sha1 = "bc0788a36b6b839fc917be0577cd14e584c71fd8"
        md5 = "1fe8b9a14f9f8435c5fb5156bcbc174e"

    condition:
        any of them
}

Rule 2: Rust Cryptographic Library Detection

rule Arsenal237_RustCrypto_ChaCha20_RSA {
    meta:
        description = "Detects malware using Rust ChaCha20 + RSA cryptographic libraries"
        author = "Threat Intelligence Team"
        date = "2026-01-27"
        malware_type = "Ransomware"
        threat_level = "CRITICAL"

    strings:
        // Rust crypto library paths (embedded in binary)
        $chacha20 = "/chacha20-0.9.1/src/lib.rs" ascii
        $rsa = "/rsa-0.9.9/src/algorithms/" ascii
        $aead = "/aead-0.5.2/src/lib.rs" ascii
        $cipher = "/cipher-0.4.4/" ascii
        $digest = "/digest-0.10.7/" ascii
        $rand = "/rand-0.8.5/" ascii

    condition:
        uint16(0) == 0x5A4D and  // PE signature
        filesize > 10MB and
        3 of them
}

Rule 3: Ransom String and Extension Detection

rule Arsenal237_Ransomware_Lockbox_Strings {
    meta:
        description = "Detects ransom messaging and .lockbox file extension"
        author = "Threat Intelligence Team"
        date = "2026-01-27"
        malware_type = "Ransomware"
        threat_level = "CRITICAL"
        confidence = "HIGH"

    strings:
        // Ransom-specific strings
        $ransom1 = "YOUR FILES HAVE BEEN ENCRYPTED!" ascii wide
        $ransom2 = "Ransom ID:" ascii wide
        $ransom3 = "Ransom ID: " ascii

        // File extension indicator
        $lockbox = ".lockbox" ascii wide

        // Operational logging strings
        $log1 = "[*] Encryptor starting..." ascii
        $log2 = "[*] Encrypting all drives..." ascii
        $log3 = "[+] Encryption complete!" ascii

    condition:
        uint16(0) == 0x5A4D and
        filesize > 10MB and filesize < 20MB and
        (2 of ($ransom*) and $lockbox) or
        (all of ($log*))
}

Rule 4: Parallel Processing and Anti-Analysis

rule Arsenal237_Rayon_AntiAnalysis {
    meta:
        description = "Detects Rayon parallel processing library and anti-analysis techniques"
        author = "Threat Intelligence Team"
        date = "2026-01-27"
        malware_type = "Ransomware"

    strings:
        // Parallel processing
        $rayon = "/rayon-1.11.0/src/" ascii
        $walkdir = "/walkdir-2.5.0/" ascii

        // Anti-analysis indicators
        $sysinfo = "/sysinfo-0.29.11/" ascii
        $vm_detect = "VMware" ascii nocase
        $vbox_detect = "VirtualBox" ascii nocase

        // Error strings indicating encryption
        $encrypt_error1 = "Failed to encrypt nonce" ascii
        $encrypt_error2 = "Failed to encrypt key" ascii
        $encrypt_error3 = "Block encryption failed" ascii

    condition:
        uint16(0) == 0x5A4D and
        filesize > 10MB and
        (all of ($rayon, $walkdir, $sysinfo)) or
        (2 of ($vm_detect, $vbox_detect, $encrypt_error*))
}

Rule 5: Network Share Enumeration Pattern

rule Arsenal237_NetworkShare_Enumeration {
    meta:
        description = "Detects malware performing network share enumeration"
        author = "Threat Intelligence Team"
        date = "2026-01-27"
        malware_type = "Ransomware"

    strings:
        // Network share operations
        $netuse = "net use" ascii
        $unc_pattern = "\\\\" ascii  // UNC path indicator
        $smb = "SMB" ascii nocase

        // Error string specific to net use execution
        $netuse_error = "Failed to execute net use" ascii

        // Folder targeting string
        $folder_option = "--folder" ascii

    condition:
        uint16(0) == 0x5A4D and
        filesize > 10MB and
        ($netuse or $netuse_error or $unc_pattern) and
        ($folder_option or "C:\\Windows\\Temp" ascii)
}

Rule 6: Comprehensive Arsenal-237 Detection

rule Arsenal237_FullTestEnc_Comprehensive {
    meta:
        description = "Comprehensive detection combining multiple Arsenal-237 indicators"
        author = "Threat Intelligence Team"
        date = "2026-01-27"
        malware_type = "Ransomware"
        threat_level = "CRITICAL"
        confidence = "HIGH"

    strings:
        // Crypto indicators (must have)
        $chacha = "/chacha20-" ascii
        $rsa_lib = "/rsa-" ascii

        // Ransom indicators (must have)
        $ransom = "YOUR FILES HAVE BEEN ENCRYPTED!" ascii wide

        // Performance/behavioral (must have at least 1)
        $rayon = "/rayon-" ascii
        $walkdir = "/walkdir-" ascii
        $sysinfo = "/sysinfo-" ascii

        // Extension (should have)
        $lockbox = ".lockbox" ascii

        // Network (should have)
        $netuse = "net use" ascii

    condition:
        uint16(0) == 0x5A4D and
        filesize > 10MB and filesize < 20MB and
        $chacha and $rsa_lib and $ransom and
        (1 of ($rayon, $walkdir, $sysinfo)) and
        ($lockbox or $netuse or "Ransom ID" ascii)
}

---

Sigma Detection Rules

Rule 1: Mass .lockbox File Creation

title: Arsenal-237 - Mass .lockbox File Creation
id: arsenal-237-lockbox-creation-sigma
date: 2026-01-27
modified: 2026-01-27
status: experimental
logsource:
    category: file_event
    product: windows
    service: sysmon
detection:
    selection:
        EventID: 11
        TargetFilename|endswith: '.lockbox'
    filter:
        Image|contains:
            - 'C:\Program Files'
            - 'C:\Program Files (x86)'
            - 'C:\Windows\System32'
            - 'C:\Windows\SysWOW64'
    timeframe: 1m
    condition: selection and not filter | count(TargetFilename) > 10
fields:
    - EventID
    - TargetFilename
    - Image
    - User
    - Computer
falsepositives:
    - Legitimate backup software with custom extensions
    - Database backup processes
level: critical

Rule 2: Unsigned Binary Executing “net use”

title: Arsenal-237 - Unsigned Binary Executing net use
id: arsenal-237-netuse-unsigned-sigma
date: 2026-01-27
logsource:
    category: process_creation
    product: windows
    service: sysmon
detection:
    selection:
        EventID: 1
        CommandLine|contains: 'net use'
        Image|notin:
            - 'C:\Windows\*'
            - 'C:\Program Files*'
        SignedStatus|endswith: 'unsigned'
    filter_admin:
        User|contains: 'SYSTEM'
        ParentImage|endswith:
            - 'svchost.exe'
            - 'lsass.exe'
    condition: selection and not filter_admin
fields:
    - EventID
    - CommandLine
    - Image
    - User
    - ParentImage
    - TargetObject
falsepositives:
    - Administrative tools
    - Batch scripts
level: high

Rule 3: Parallel WriteFile Operations

title: Arsenal-237 - Parallel Multi-threaded File Operations
id: arsenal-237-parallel-writes-sigma
date: 2026-01-27
logsource:
    category: file_event
    product: windows
    service: sysmon
detection:
    selection:
        EventID: 11
        Image|notin:
            - 'C:\Program Files*'
            - 'C:\Windows\*'
    filter_system:
        User: 'SYSTEM'
    aggregation:
        by:
            - Image
            - TargetFilename
    condition: selection and not filter_system | count() > 50 within 60s
fields:
    - EventID
    - Image
    - TargetFilename
    - User
    - Computer
falsepositives:
    - Legitimate backup software
    - Database maintenance operations
level: critical

Rule 4: GetLogicalDrives API Enumeration

title: Arsenal-237 - All Drives Enumeration (GetLogicalDrives)
id: arsenal-237-getlogicaldrives-sigma
date: 2026-01-27
logsource:
    category: file_event
    product: windows
    service: sysmon
detection:
    selection:
        EventID: 11
        TargetFilename|contains:
            - 'A:\'
            - 'B:\'
            - 'C:\'
            - 'D:\'
            - 'E:\'
        Image|notin:
            - 'C:\Windows\*'
            - 'C:\Program Files*'
    aggregation:
        by:
            - Image
            - User
    condition: selection | count(TargetFilename) > 10 within 60s
fields:
    - EventID
    - Image
    - TargetFilename
    - User
level: high

Rule 5: Cryptocurrency Library Detection

title: Arsenal-237 - Rust Cryptographic Libraries in Process Memory
id: arsenal-237-crypto-libs-sigma
date: 2026-01-27
logsource:
    category: image_load
    product: windows
    service: sysmon
detection:
    selection:
        EventID: 7
        ImageLoaded|contains:
            - 'chacha20'
            - 'rsa'
            - 'aead'
            - 'rayon'
    filter:
        Image|endswith:
            - '.exe'
        Signed: 'false'
    condition: selection and filter
fields:
    - EventID
    - Image
    - ImageLoaded
    - ProcessId
level: high

---

KQL (Kusto Query Language) - Azure Sentinel / Microsoft Defender

Query 1: Detect .lockbox File Creation

// Detect mass .lockbox file creation
DeviceFileEvents
| where FileName endswith ".lockbox"
| where ActionType == "FileCreated"
| where InitiatingProcessFileName !in ("System", "svchost.exe", "csrss.exe", "SearchIndexer.exe")
| where InitiatingProcessFileName !contains "Windows"
| where InitiatingProcessFolderPath !startswith "C:\\Windows\\"
| where InitiatingProcessFolderPath !startswith "C:\\Program Files"
| summarize
    FileCount = dcount(FileName),
    FileList = make_set(FileName, 20),
    FirstSeen = min(Timestamp),
    LastSeen = max(Timestamp)
    by DeviceName, InitiatingProcessName, InitiatingProcessSHA256
| where FileCount > 10
| project TimeGenerated=LastSeen, DeviceName, InitiatingProcessName, FileCount, FileList

Query 2: Unsigned Binary Executing net use

// Detect unsigned binary executing net use
DeviceProcessEvents
| where ProcessCommandLine contains "net use"
| where SignerName == "" or SignerName == "unsigned"
| where ProcessFileName !contains "C:\\Windows"
| where ProcessFileName !contains "C:\\Program Files"
| join kind=inner (
    DeviceFileEvents
    | where FileName == "full_test_enc.exe" or FileName contains "test_enc"
    ) on DeviceName
| project TimeGenerated, DeviceName, ProcessCommandLine, ProcessFileName, ProcessSHA256
| limit 100

Query 3: Mass File Modifications in Short Timeframe

// Detect rapid sequential file modifications (ransomware pattern)
DeviceFileEvents
| where ActionType == "FileCreated" or ActionType == "FileModified"
| where InitiatingProcessFileName !contains "Windows"
| where InitiatingProcessFileName !contains "System"
| summarize
    FileCount = dcount(FileName),
    ProcessName = any(InitiatingProcessFileName),
    ProcessPath = any(InitiatingProcessFolderPath)
    by DeviceName, bin(Timestamp, 60s)
| where FileCount > 100
| project Timestamp, DeviceName, ProcessName, FileCount

Query 4: Parallel WriteFile Operations Detection

// Detect parallel multi-threaded file operations
DeviceFileEvents
| where ActionType == "FileCreated"
| where InitiatingProcessFileName !contains "System"
| where InitiatingProcessFileName !contains "Windows"
| summarize
    FileCount = dcount(FileName),
    UniqueHashes = dcount(InitiatingProcessSHA256),
    TimeRange = max(Timestamp) - min(Timestamp)
    by DeviceName, InitiatingProcessName, bin(Timestamp, 10s)
| where FileCount > 20 and TimeRange < 60s
| project Timestamp, DeviceName, InitiatingProcessName, FileCount

Query 5: Search for Arsenal-237 File Hashes

// Search for Arsenal-237 ransomware by known hashes
DeviceFileEvents
| where (SHA256 == "4d1fe7b54a0ce9ce2082c167b662ec138b890e3f305e67bdc13a5e9a24708518" or
         SHA1 == "bc0788a36b6b839fc917be0577cd14e584c71fd8" or
         MD5 == "1fe8b9a14f9f8435c5fb5156bcbc174e")
| project TimeGenerated, DeviceName, FileName, FolderPath, SHA256, MD5
| union (
    DeviceProcessEvents
    | where (SHA256 == "4d1fe7b54a0ce9ce2082c167b662ec138b890e3f305e67bdc13a5e9a24708518" or
             ProcessSHA256 == "4d1fe7b54a0ce9ce2082c167b662ec138b890e3f305e67bdc13a5e9a24708518")
    | project TimeGenerated, DeviceName, ProcessName, ProcessCommandLine, ProcessFolderPath
    )

Query 6: Network Share Write Activity from Unsigned Binary

// Detect unsigned binary writing to network shares
DeviceFileEvents
| where FileName endswith ".lockbox"
| where ActionType == "FileCreated" or ActionType == "FileModified"
| where FolderPath startswith "\\\\"  // UNC path indicator
| where InitiatingProcessFileName !contains "backup"
| where InitiatingProcessFileName !contains "System"
| summarize
    FileCount = dcount(FileName),
    ShareList = make_set(FolderPath, 10)
    by DeviceName, InitiatingProcessName, InitiatingProcessSHA256
| where FileCount > 5
| project DeviceName, InitiatingProcessName, FileCount, ShareList

Query 7: VM/Debugger Evasion Attempts

// Detect VM and debugger detection attempts
DeviceEvents
| where EventType == "SetUnhandledExceptionFilter" or
        EventType == "AddVectoredExceptionHandler" or
        EventType == "QueryPerformanceCounter"  // Timing checks
| where InitiatingProcessFileName !contains "Windows"
| where InitiatingProcessFileName !contains "System"
| join kind=inner (
    DeviceFileEvents
    | where FileName == "full_test_enc.exe"
    ) on DeviceName
| project TimeGenerated, DeviceName, EventType, InitiatingProcessName

---

Splunk SPL (Search Processing Language)

Search 1: Detect .lockbox File Creation

index=main source=sysmon EventCode=11 TargetFilename="*.lockbox"
| search NOT (Image="*\\System*" OR Image="*\\Windows\\*" OR Image="*\\Program Files*")
| stats count by host, Image, TargetFilename
| where count > 10
| table _time, host, Image, TargetFilename, count

Search 2: Network Share Enumeration via net use

index=main source=sysmon EventCode=1 CommandLine="*net use*"
| search NOT (Image="*\\Windows\\*" OR Image="*\\System*")
| search Signed=false OR SignedStatus=Unsigned
| table _time, host, CommandLine, Image, User, ParentImage

Search 3: Rapid File Modifications

index=main source=sysmon EventCode=11
| search NOT (Image="*\\Windows\\*" OR Image="*\\System*")
| stats count by host, Image, _time
| where count > 50
| alert

Search 4: Arsenal-237 Hash Detection

index=main (
    SHA256="4d1fe7b54a0ce9ce2082c167b662ec138b890e3f305e67bdc13a5e9a24708518" OR
    SHA1="bc0788a36b6b839fc917be0577cd14e584c71fd8" OR
    MD5="1fe8b9a14f9f8435c5fb5156bcbc174e"
)
| table _time, host, FileName, FilePath, SHA256, EventCode

---

Elastic Detection Rules

Rule 1: Arsenal-237 Ransomware - .lockbox Extension

{
  "author": ["Threat Intelligence Team"],
  "description": "Detects creation of files with .lockbox extension, indicating Arsenal-237 ransomware activity",
  "enabled": true,
  "false_positives": ["Legitimate backup software"],
  "from": "now-10m",
  "index": ["logs-endpoint.file-*"],
  "interval": "5m",
  "language": "kuery",
  "name": "Arsenal-237 - .lockbox File Creation",
  "query": "host.os.type:windows and event.action:creation and file.name:*.lockbox",
  "risk_score": 95,
  "rule_id": "arsenal-237-lockbox-creation",
  "severity": "critical",
  "tags": ["ransomware", "arsenal-237", "lockbox"],
  "type": "query",
  "aggregation": {
    "field": "host.name",
    "terms_size": 10
  }
}

Rule 2: Unsigned Binary Network Share Access

{
  "author": ["Threat Intelligence Team"],
  "description": "Detects unsigned binaries accessing network shares, potential Arsenal-237 lateral movement",
  "enabled": true,
  "from": "now-10m",
  "index": ["logs-endpoint.process-*"],
  "interval": "5m",
  "language": "kuery",
  "name": "Arsenal-237 - Unsigned Binary UNC Path Access",
  "query": "process.code_signature.status:unsigned and process.command_line:(*\\\\\\\\* or *net\\ use*) and not process.executable:(*Windows* or *Program\\ Files*)",
  "risk_score": 85,
  "rule_id": "arsenal-237-unsigned-unc",
  "severity": "high"
}

Rule 3: Rayon Library and Cryptographic Operations

{
  "author": ["Threat Intelligence Team"],
  "description": "Detects loading of Rayon parallel processing library with cryptographic operations",
  "enabled": true,
  "from": "now-10m",
  "index": ["logs-endpoint.library-*"],
  "interval": "5m",
  "language": "kuery",
  "name": "Arsenal-237 - Rayon Parallel Processing Library",
  "query": "dll.name:*rayon* and (process.name:*chacha* or process.name:*rsa*)",
  "risk_score": 80,
  "rule_id": "arsenal-237-rayon",
  "severity": "high"
}

---

EDR Behavioral Correlation Rules

Rule 1: Arsenal-237 Complete Attack Chain

IF
  (Process.Unsigned == TRUE) AND
  (Process.FileSize > 10MB) AND
  (Process.FileSize < 20MB) AND
  (Process.Language == "Rust" OR Binary.Contains("chacha20") OR Binary.Contains("/rsa-")) AND
  (CommandLine.Contains("net use")) AND
  (FileCreate.Extension == ".lockbox" AND FileCreate.Count >= 10 WITHIN 60 seconds) AND
  (API.Call == "GetLogicalDrives" OR API.Call == "CreateProcessW")
THEN
  ALERT: CRITICAL - Arsenal-237 Ransomware Activity Detected
  ACTIONS:
    - Kill Process Immediately
    - Isolate Network Interface
    - Preserve Memory Image
    - Alert Incident Response Team
  CONFIDENCE: CRITICAL (99%)

Rule 2: Ransomware Encryption Pattern

IF
  (FileCreate.Count > 50 WITHIN 60s) AND
  (FileCreate.Pattern == "*.lockbox") AND
  (Process.CPU.Usage > 80%) AND
  (Process.Thread.Count > 10) AND
  (Process.Unsigned == TRUE) AND
  (FileModify.Delete == TRUE)  // Original file deleted after encryption
THEN
  ALERT: HIGH - Ransomware Encryption Pattern Detected
  ACTIONS:
    - Kill Process
    - Isolate System
  CONFIDENCE: HIGH (90%)

Rule 3: Lateral Movement via SMB

IF
  (Process.CommandLine.Contains("net use")) AND
  (Network.SMB.Write.Count > 100) AND
  (Network.SMB.Share.AccessedCount > 5) AND
  (FileCreate.Extension == ".lockbox" ON NETWORK_SHARE)
THEN
  ALERT: CRITICAL - Ransomware Lateral Movement Detected
  ACTIONS:
    - Kill Process
    - Block SMB Traffic from Source
    - Scan Destination Shares
  CONFIDENCE: CRITICAL (95%)

---

Advanced Threat Hunting Queries

Hunt 1: Identify Rust Binaries with Cryptographic Libraries

index=main source=sysmon EventCode=11
| search (FileName="*chacha*" OR FileName="*rsa*")
| stats values(Image) as processes by host
| search processes="*.exe" AND processes NOT "*Windows*"
| table host, processes

Hunt 2: Find All Binaries with .lockbox Extension Association

DeviceFileEvents
| where FileName endswith ".lockbox"
| distinct InitiatingProcessName, InitiatingProcessSHA256, InitiatingProcessFolderPath
| project ProcessName=InitiatingProcessName, ProcessHash=InitiatingProcessSHA256, ProcessPath=InitiatingProcessFolderPath

Hunt 3: Identify Systems with Multiple Drive Access

index=main source=sysmon EventCode=11
| search FileName="*:\\"
| stats count as DriveAccessCount by Image, host
| where DriveAccessCount > 3
| table host, Image, DriveAccessCount

Hunt 4: Timeline Reconstruction of Ransomware Activity

DeviceFileEvents
| where FileName endswith ".lockbox" or (ActionType == "FileCreated" and TargetFilename contains "Ransom")
| order by Timestamp asc
| extend Activity = case(
    FileName endswith ".lockbox", "File Encrypted",
    ActionType == "FileDeleted", "Original Deleted",
    ActionType == "FileModified", "File Modified",
    "Other"
  )
| project Timestamp, DeviceName, FileName, Activity, InitiatingProcessName

---

Network Detection Signatures

Suricata Rule: Arsenal-237 SMB Share Enumeration

alert smb $HOME_NET any -> $EXTERNAL_NET any (
    msg:"Arsenal-237 SMB Share Enumeration Attempt";
    flow:to_server,established;
    content:"net use";
    http_client_body;
    classtype:trojan-activity;
    sid:1000001;
    rev:1;
)

Snort Rule: RDP Lateral Movement Post-Encryption

alert tcp $HOME_NET any -> $HOME_NET 3389 (
    msg:"Ransomware RDP Lateral Movement";
    flow:to_server,established;
    content:"RDP";
    classtype:suspicious-login;
    sid:1000002;
    rev:1;
)

---

Incident Response Playbook Triggers

Automated Response on Arsenal-237 Detection

Priority 1 (Immediate - <5 minutes):

• Kill process (full_test_enc.exe or unsigned 15MB binary)
• Isolate network interface
• Preserve memory dump
• Alert incident response team

Priority 2 (Urgent - <15 minutes):

• Scan file servers for .lockbox files
• Check system for lateral movement
• Verify backup system isolation
• Begin incident response procedures

Priority 3 (High - <30 minutes):

• Forensic analysis of affected system
• Determine infection timeline
• Assess data encryption extent
• Make rebuild vs. cleanup decision

---

Detection Tuning Parameters

False Positive Reduction

Exclude from alerting:

• System processes (System.exe, csrss.exe, svchost.exe)
• Windows processes (WindowsUpdate, SearchIndexer)
• Signed executables (unless suspicious command line)
• Backup software (if specifically whitelisted)

Context sensitivity:

• Adjust .lockbox detection threshold based on organization size
• Set FileCreate count thresholds for environment (baseline: 10+ per minute = alert)
• Adjust time windows for multi-threaded operations (60 seconds typical)

Performance Considerations

• .lockbox detection has minimal performance impact (simple extension match)
• Multi-threaded file operation detection requires EDR telemetry collection
• YARA scanning should use hash-based rule first (fastest) before complex patterns
• KQL/Splunk queries benefit from indexed fields (FileName, EventCode, CommandLine)