{ "technique_id": "T1573", "name": "Encrypted Channel", "priority": "high", "status": "draft", "version": "0.1.0", "last_reviewed": "2026-07-23", "generated_by": "SOC Response Atlas by Basyrix", "tactics": [ "Command and Control" ], "platforms": [ "ESXi", "Linux", "macOS", "Network Devices", "Windows" ], "summary": "Adversaries may employ an encryption algorithm to conceal command and control traffic rather than relying on any inherent protections provided by a communication protocol. Despite the use of a secure algorithm, these implementations may be vulnerable to reverse engineering if secret keys are encoded and/or generated within malware samples/configuration files.", "soc_recommendation": "Investigate Encrypted Channel activity in the context of Command and Control: confirm scope, affected host/identity, and whether it matches expected administrative behaviour before deciding this is benign.", "d3fend_mappings": [ { "id": "D3-FA", "name": "File Analysis", "relationship": "detect", "practical_action": "Monitor for File Analysis indicators relevant to this technique.", "tooling": [ "Defender for Endpoint" ] }, { "id": "D3-FE", "name": "File Encryption", "relationship": "harden", "practical_action": "Apply File Encryption to reduce this technique's viability before an incident occurs.", "tooling": [ "Defender for Endpoint" ] }, { "id": "D3-FEV", "name": "File Eviction", "relationship": "evict", "practical_action": "Use File Eviction to remove the adversary's foothold once this technique is confirmed.", "tooling": [ "Defender for Endpoint" ] }, { "id": "D3-CF", "name": "Content Filtering", "relationship": "isolate", "practical_action": "Apply Content Filtering to contain the blast radius once this technique is observed.", "tooling": [ "Defender for Endpoint" ] } ], "investigation_steps": { "microsoft": [ "Review Defender for Endpoint / Defender XDR alerts and timeline for the affected host or identity.", "Check Sentinel analytics rules and incidents correlated with this technique.", "Review Entra ID sign-in and audit logs if the technique involves an identity or cloud resource." ], "generic": [ "Confirm whether the observed encrypted channel activity matches expected administrative or application behaviour.", "Identify the host, account, or resource where the activity occurred and its business criticality.", "Check for related alerts before and after this activity to reconstruct the broader intrusion timeline.", "Real detection reference: \"CYFIRMA - High severity Command & Control Network Indicators with Block Recommendation Rule\" -- \"This analytics rule detects network-based indicators identified by CYFIRMA threat intelligence as associated with Command & Control (C2) infrastructure. These may represent attacker-controlled endpoints used to maintain persistence, exfiltrate data, or receive commands from malware-infected hosts.\"" ] }, "evidence_to_collect": [ "Host or resource affected", "Account or identity involved", "Timestamp of the activity", "Related process, file, or network artifact", "Any preceding or follow-on alerts" ], "response_actions": [ { "name": "Contain the affected host or account", "category": "Containment", "risk": "Medium", "automation_safe": false, "approval_required": true, "tool": "Defender for Endpoint / Entra ID", "notes": "Requires approval -- confirm malicious intent before isolating a host or disabling an account." }, { "name": "Collect and preserve evidence", "category": "Investigation", "risk": "Low", "automation_safe": true, "approval_required": false, "tool": "Defender for Endpoint", "notes": "Safe -- read-only evidence collection." } ], "queries": { "kql": [ { "name": "6b61b716-afd9-4f6c-ad00-965d5987cafd — CYFIRMA - High severity Command & Control Network Indicators with Block Recommendation Rule", "description": "\"This analytics rule detects network-based indicators identified by CYFIRMA threat intelligence as associated with Command & Control (C2) infrastructure. These may represent attacker-controlled endpoints used to maintain persistence, exfiltrate data, or receive commands from malware-infected hosts.\" (Source: Microsoft's official Azure-Sentinel Detections (MIT licensed), mapped via sub-technique T1573.001.)", "query": "// Network Indicators query with Block Recommended Action and C2 Roles\nlet timeFrame= 5m;\nCyfirmaIndicators_CL \n| where ConfidenceScore >= 80\n and TimeGenerated between (ago(timeFrame) .. now())\n and pattern !contains 'file:hashes' and RecommendedActions has 'Block' and (Roles contains 'c2' or Roles contains 'Command & Control')\n| extend IPv4 = extract(@\"ipv4-addr:value\\s*=\\s*'([^']+)'\", 1, pattern)\n| extend IPv6 = extract(@\"ipv6-addr:value\\s*=\\s*'([^']+)'\", 1, pattern)\n| extend URL = extract(@\"url:value\\s*=\\s*'([^']+)'\", 1, pattern)\n| extend Domain = extract(@\"domain-name:value\\s*=\\s*'([^']+)'\", 1, pattern)\n| extend parsed = parse_json(extensions)\n| extend extensionKeys = bag_keys(parsed)\n| mv-expand extensionKeys\n| extend extensionKeyStr = tostring(extensionKeys)\n| extend ext = parsed[extensionKeyStr]\n| extend props = ext.properties\n| extend \n extension_id = extensionKeyStr,\n ASN_Owner = props.asn_owner,\n ASN = props.asn,\n ProviderName = 'CYFIRMA',\n ProductName = 'DeCYFIR/DeTCT'\n| project\n IPv4,\n IPv6,\n URL,\n Domain,\n ThreatActors,\n RecommendedActions,\n Sources,\n Roles,\n Country,\n IPAbuse,\n name,\n Description,\n ConfidenceScore,\n IndicatorID,\n created,\n modified,\n valid_from,\n Tags,\n ThreatType,\n TimeGenerated,\n SecurityVendors,\n ProductName,\n ProviderName" }, { "name": "6d8fb3fe-2501-4103-8137-34261fa3a596 — CYFIRMA - High severity Command & Control Network Indicators with Monitor Recommendation Rule", "description": "\"This analytics rule detects network-based indicators identified by CYFIRMA threat intelligence as associated with Command & Control (C2) infrastructure. These may represent attacker-controlled endpoints used to maintain persistence, exfiltrate data, or receive commands from malware-infected hosts.\" (Source: Microsoft's official Azure-Sentinel Detections (MIT licensed), mapped via sub-technique T1573.001.)", "query": "// Network Indicators query with Monitor Recommended Action And C2 Roles\nlet timeFrame= 5m;\nCyfirmaIndicators_CL \n| where ConfidenceScore >= 80\n and TimeGenerated between (ago(timeFrame) .. now())\n and pattern !contains 'file:hashes' and RecommendedActions has 'Monitor' and (Roles contains 'c2' or Roles contains 'Command & Control')\n| extend IPv4 = extract(@\"ipv4-addr:value\\s*=\\s*'([^']+)'\", 1, pattern)\n| extend IPv6 = extract(@\"ipv6-addr:value\\s*=\\s*'([^']+)'\", 1, pattern)\n| extend URL = extract(@\"url:value\\s*=\\s*'([^']+)'\", 1, pattern)\n| extend Domain = extract(@\"domain-name:value\\s*=\\s*'([^']+)'\", 1, pattern)\n| extend parsed = parse_json(extensions)\n| extend extensionKeys = bag_keys(parsed)\n| mv-expand extensionKeys\n| extend extensionKeyStr = tostring(extensionKeys)\n| extend ext = parsed[extensionKeyStr]\n| extend props = ext.properties\n| extend \n extension_id = extensionKeyStr,\n ASN_Owner = props.asn_owner,\n ASN = props.asn,\n ProviderName = 'CYFIRMA',\n ProductName = 'DeCYFIR/DeTCT'\n| project\n IPv4,\n IPv6,\n URL,\n Domain,\n ThreatActors,\n RecommendedActions,\n Sources,\n Roles,\n Country,\n IPAbuse,\n name,\n Description,\n ConfidenceScore,\n IndicatorID,\n created,\n modified,\n valid_from,\n Tags,\n ThreatType,\n TimeGenerated,\n SecurityVendors,\n ProductName,\n ProviderName" }, { "name": "ef88eb96-861c-43a0-ab16-f3835a97c928 — Powershell Empire Cmdlets Executed in Command Line", "description": "This query identifies use of PowerShell Empire's cmdlets within the command line data of the PowerShell process, indicating potential use of the post-exploitation tool.' (Source: Microsoft's official Azure-Sentinel Detections (MIT licensed), mapped via sub-technique T1573.002.)", "query": "let regexEmpire = tostring(toscalar(externaldata(cmdlets:string)[@\"https://raw.githubusercontent.com/Azure/Azure-Sentinel/master/Sample%20Data/Feeds/EmpireCommandString.txt\"] with (format=\"txt\")));\n(union isfuzzy=true\n (SecurityEvent\n| where EventID == 4688\n//consider filtering on filename if perf issues occur\n//where FileName in~ (\"powershell.exe\",\"powershell_ise.exe\",\"pwsh.exe\")\n| where not(ParentProcessName has_any ('gc_worker.exe', 'gc_service.exe'))\n| where CommandLine has \"-encodedCommand\"\n| parse kind=regex flags=i CommandLine with * \"-EncodedCommand \" encodedCommand\n| extend encodedCommand = iff(encodedCommand has \" \", tostring(split(encodedCommand, \" \")[0]), encodedCommand)\n// Note: currently the base64_decode_tostring function is limited to supporting UTF8\n| extend decodedCommand = translate('\\0','', base64_decode_tostring(substring(encodedCommand, 0, strlen(encodedCommand) - (strlen(encodedCommand) %8)))), encodedCommand, CommandLine , strlen(encodedCommand)\n| extend EfectiveCommand = iff(isnotempty(encodedCommand), decodedCommand, CommandLine)\n| where EfectiveCommand matches regex regexEmpire\n| project timestamp = TimeGenerated, Computer, SubjectUserName, SubjectDomainName, FileName = Process, EfectiveCommand, decodedCommand, encodedCommand, CommandLine, ParentProcessName\n| extend HostName = split(Computer, '.', 0)[0], DnsDomain = strcat_array(array_slice(split(Computer, '.'), 1, -1), '.')\n),\n(WindowsEvent\n| where EventID == 4688\n| where EventData has_any (\"-encodedCommand\", \"powershell.exe\",\"powershell_ise.exe\",\"pwsh.exe\")\n| where not(EventData has_any ('gc_worker.exe', 'gc_service.exe'))\n//consider filtering on filename if perf issues occur\n//extend NewProcessName = tostring(EventData.NewProcessName)\n//extend Process=tostring(split(NewProcessName, '\\\\')[-1])\n//FileName = Process\n//where FileName in~ (\"powershell.exe\",\"powershell_ise.exe\",\"pwsh.exe\")\n| extend ParentProcessName = tostring(EventData.ParentProcessName)\n| where not(ParentProcessName has_any ('gc_worker.exe', 'gc_service.exe'))\n| extend CommandLine = tostring(EventData.CommandLine)\n| where CommandLine has \"-encodedCommand\"\n| parse kind=regex flags=i CommandLine with * \"-EncodedCommand \" encodedCommand\n| extend encodedCommand = iff(encodedCommand has \" \", tostring(split(encodedCommand, \" \")[0]), encodedCommand)\n// Note: currently the base64_decode_tostring function is limited to supporting UTF8\n| extend decodedCommand = translate('\\0','', base64_decode_tostring(substring(encodedCommand, 0, strlen(encodedCommand) - (strlen(encodedCommand) %8)))), encodedCommand, CommandLine , strlen(encodedCommand)\n| extend EfectiveCommand = iff(isnotempty(encodedCommand), decodedCommand, CommandLine)\n| where EfectiveCommand matches regex regexEmpire\n| extend SubjectUserName = tostring(EventData.SubjectUserName)\n| extend SubjectDomainName = tostring(EventData.SubjectDomainName)\n| extend NewProcessName = tostring(EventData.NewProcessName)\n| extend Process=tostring(split(NewProcessName, '\\\\')[-1])\n| project timestamp = TimeGenerated, Computer, SubjectUserName, SubjectDomainName, FileName = Process, EfectiveCommand, decodedCommand, encodedCommand, CommandLine, ParentProcessName\n| extend HostName = split(Computer, '.', 0)[0], DnsDomain = strcat_array(array_slice(split(Computer, '.'), 1, -1), '.')\n))" } ], "spl": [], "esql": [ { "name": "ad5a3757-c872-4719-8c72-12d3f08db655 — Openssl Client or Server Activity", "description": "(EQL) This rule identifies when the openssl client or server is used to establish a connection. Attackers may use openssl to establish a secure connection to a remote server or to create a secure server to receive connections. This activity may be used to exfiltrate data or establish a command and control channel. (Source: Elastic's official detection-rules repository (Elastic License v2).)", "query": "process where host.os.type == \"linux\" and event.type == \"start\" and event.action in (\"exec\", \"exec_event\", \"start\") and\nprocess.name == \"openssl\" and (\n (\n process.args == \"s_client\" and process.args : (\"-connect\", \"*:*\") and\n process.args in (\n \"sh\", \"dash\", \"bash\", \"zsh\",\n \"/bin/sh\", \"/bin/dash\", \"/bin/bash\", \"/bin/zsh\",\n \"/usr/bin/sh\", \"/usr/bin/dash\", \"/usr/bin/bash\", \"/usr/bin/zsh\",\n \"/usr/local/bin/sh\", \"/usr/local/bin/dash\", \"/usr/local/bin/bash\", \"/usr/local/bin/zsh\"\n ) and not process.args == \"-showcerts\"\n ) or\n (process.args == \"s_server\" and process.args == \"-port\")\n) and\nnot process.parent.executable in (\n \"/pro/xymon/client/ext/awsXymonCheck.sh\", \"/opt/antidot-svc/nrpe/plugins/check_cert\", \"/etc/zabbix/scripts/check_dane_tlsa.sh\"\n)" }, { "name": "e3cf38fa-d5b8-46cc-87f9-4a7513e4281d — Connection to Commonly Abused Free SSL Certificate Providers", "description": "(EQL) Identifies unusual processes connecting to domains using known free SSL certificates. Adversaries may employ a known encryption algorithm to conceal command and control traffic. (Source: Elastic's official detection-rules repository (Elastic License v2).)", "query": "network where host.os.type == \"windows\" and network.protocol == \"dns\" and\n /* Add new free SSL certificate provider domains here */\n dns.question.name : (\"*letsencrypt.org\", \"*.sslforfree.com\", \"*.zerossl.com\", \"*.freessl.org\") and\n\n /* Native Windows process paths that are unlikely to have network connections to domains secured using free SSL certificates */\n process.executable : (\"C:\\\\Windows\\\\System32\\\\*.exe\",\n \"C:\\\\Windows\\\\System\\\\*.exe\",\n\t \"C:\\\\Windows\\\\SysWOW64\\\\*.exe\",\n\t\t \"C:\\\\Windows\\\\Microsoft.NET\\\\Framework*\\\\*.exe\",\n\t\t \"C:\\\\Windows\\\\explorer.exe\",\n\t\t \"C:\\\\Windows\\\\notepad.exe\") and\n\n /* Insert noisy false positives here */\n not process.name : (\"svchost.exe\", \"MicrosoftEdge*.exe\", \"msedge.exe\")" } ] }, "automation": { "safe": [ "Add recommendation as Sentinel incident comment.", "Run enrichment queries.", "Create ServiceNow SecOps task." ], "approval_required": [ "Contain or disable the affected host/account.", "Any change to production configuration." ] }, "escalation_criteria": [ "Encrypted Channel activity observed on a privileged account or critical system.", "Activity follows or precedes other suspicious behaviour in the same investigation.", "Automated triage cannot confidently rule out malicious intent." ], "false_positive_considerations": [ "Legitimate administrative or maintenance activity matching this pattern.", "Approved security testing or red team exercise.", "Known benign software producing similar telemetry." ], "confluence": { "title": "T1573 - Encrypted Channel Response Guidance", "labels": [ "mitre", "attack", "d3fend", "secops", "basyrix" ], "sections": [ "summary", "d3fend_mappings", "investigation_steps", "response_actions", "queries", "automation", "escalation_criteria", "false_positive_considerations" ] } }