Attack Ent T1505 005 Terminal Services Dll

MITRE ATT&CK T1505.005: Terminal Services DLL

When to use this skill

Use this skill when the task involves T1505.005, Terminal Services DLL, enterprise ATT&CK, TTP mapping, detection engineering, hunting, incident-response enrichment, control validation, or authorized adversary-emulation planning. Treat it as a defensive analysis aid: keep outputs focused on understanding, detecting, mitigating, and safely validating this ATT&CK sub-technique.

Technique context

• ATT&CK domain: enterprise
• ATT&CK ID: T1505.005
• Technique name: Terminal Services DLL
• Type: sub-technique
• ATT&CK URL: https://attack.mitre.org/techniques/T1505/005
• Tactics: persistence
• Platforms: Windows
• Required permissions: Not specified
• Effective permissions: Not specified
• Defenses bypassed: Not specified

ATT&CK description

Adversaries may abuse components of Terminal Services to enable persistent access to systems. Microsoft Terminal Services, renamed to Remote Desktop Services in some Windows Server OSs as of 2022, enable remote terminal connections to hosts. Terminal Services allows servers to transmit a full, interactive, graphical user interface to clients via RDP.(Citation: Microsoft Remote Desktop Services)

Windows Services that are run as a "generic" process (ex: svchost.exe) load the service's DLL file, the location of which is stored in a Registry entry named ServiceDll.(Citation: Microsoft System Services Fundamentals) The termsrv.dll file, typically stored in %SystemRoot%\System32\, is the default ServiceDll value for Terminal Services in HKLM\System\CurrentControlSet\services\TermService\Parameters\.

Adversaries may modify and/or replace the Terminal Services DLL to enable persistent access to victimized hosts.(Citation: James TermServ DLL) Modifications to this DLL could be done to execute arbitrary payloads (while also potentially preserving normal termsrv.dll functionality) as well as to simply enable abusable features of Terminal Services. For example, an adversary may enable features such as concurrent Remote Desktop Protocol sessions by either patching the termsrv.dll file or modifying the ServiceDll value to point to a DLL that provides increased RDP functionality.(Citation: Windows OS Hub RDP)(Citation: RDPWrap Github) On a non-server Windows OS this increased functionality may also enable an adversary to avoid Terminal Services prompts that warn/log out users of a system when a new RDP session is created.

Agent workflow

1. Clarify scope: identify the system, asset class, log sources, cloud or endpoint platform, and whether the user wants triage, detection, coverage assessment, or safe emulation planning.
2. Load bundled resources as needed: use references/technique-profile.json for structured metadata, references/detection-and-mitigation.md for triage and telemetry guidance, references/known-threat-context.md for ATT&CK relationship context, and templates/ for repeatable outputs.
3. Map observations to ATT&CK: compare the user's evidence to the ATT&CK description, tactics, platforms, and known procedure patterns before asserting a match.
4. Produce defensive outputs: prioritize hypotheses, telemetry requirements, detection logic ideas, validation steps, containment guidance, and mitigations.
5. Preserve uncertainty: distinguish confirmed evidence, plausible indicators, assumptions, and gaps. Recommend what to collect next.
6. Stay safe: do not provide malware, credential theft, persistence, evasion, destructive automation, or unauthorized exploitation instructions. For adversary emulation, keep steps bounded to approved lab or control-validation contexts and omit operational abuse details.

Bundled resources

• references/technique-profile.json: machine-readable ATT&CK metadata for this technique.
• references/detection-and-mitigation.md: detection notes, telemetry checklist, triage questions, mitigation candidates, and false-positive considerations.
• references/known-threat-context.md: ATT&CK relationship context with attribution cautions.
• templates/detection-brief.md: detection engineering brief template.
• templates/hunt-plan.md: threat hunt plan template.
• templates/incident-response-note.md: incident response note template.
• templates/coverage-assessment.md: ATT&CK coverage assessment template.
• scripts/render_brief.py: local helper that renders a Markdown defensive brief from technique-profile.json.
• assets/output-schema.json: JSON schema for structured technique analysis outputs.

To generate a quick brief, run python scripts/render_brief.py --output brief.md from inside this skill directory, or adapt the templates directly.

Detection guidance

No ATT&CK detection guidance was present in the source STIX object.

Useful telemetry and data sources

• Not specified in the STIX object.

Mitigations to consider

• Audit
• Restrict Registry Permissions

Known threat context

Use these examples only as contextual leads, not as proof that an observed event is this technique:

• No group or software uses relationships were included for this technique in the source STIX bundle.

Recommended output pattern

When responding with this skill, structure the answer as:

• Assessment: whether the evidence supports this ATT&CK mapping and why.
• Evidence: specific indicators, logs, behaviors, and assumptions.
• Detection: telemetry sources, analytic logic, and tuning considerations.
• Response: containment, eradication, recovery, and validation actions.
• Coverage gaps: missing logs, sensors, controls, or environmental details.
• References: include the ATT&CK URL and any user-provided evidence references.