# Attack Ent T1556 005 Reversible Encryption

> Analyze MITRE ATT&CK T1556.005 Reversible Encryption in the enterprise matrix. Use for TTP triage, detection engineering, hunting, defensive emulation planning, mitigations, incident response mapping, ATT&CK coverage, or questions mentioning T1556.005, Reversible Encryption, or enterprise ATT&CK. An adversary may abuse Active Directory authentication encryption properties to gain access to credentials on Windows systems.

- Skill: `santosomar/attack-ent-t1556-005-reversible-encryption` (Agent Skill, multi-file: 11 files)
- Install (CLI): `npx skillmds@latest add santosomar/attack-ent-t1556-005-reversible-encryption`
- Raw SKILL.md: https://api.skillmd.com/api/skills/santosomar/attack-ent-t1556-005-reversible-encryption/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- License: MITRE ATT&CK Terms of Use apply to ATT&CK-derived content. See h
- Author: santosomar (https://skillmd.com/u/santosomar)
- Updated: 2026-09-22
- Page: https://skillmd.com/skills/santosomar/attack-ent-t1556-005-reversible-encryption

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# MITRE ATT&CK T1556.005: Reversible Encryption

## When to use this skill

Use this skill when the task involves T1556.005, Reversible Encryption, 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: T1556.005
- Technique name: Reversible Encryption
- Type: sub-technique
- ATT&CK URL: https://attack.mitre.org/techniques/T1556/005
- Tactics: credential-access, defense-impairment, persistence
- Platforms: Windows
- Required permissions: Not specified
- Effective permissions: Not specified
- Defenses bypassed: Not specified

## ATT&CK description

An adversary may abuse Active Directory authentication encryption properties to gain access to credentials on Windows systems. The <code>AllowReversiblePasswordEncryption</code> property specifies whether reversible password encryption for an account is enabled or disabled. By default this property is disabled (instead storing user credentials as the output of one-way hashing functions) and should not be enabled unless legacy or other software require it.(Citation: store_pwd_rev_enc)

If the property is enabled and/or a user changes their password after it is enabled, an adversary may be able to obtain the plaintext of passwords created/changed after the property was enabled. To decrypt the passwords, an adversary needs four components:

1. Encrypted password (<code>G$RADIUSCHAP</code>) from the Active Directory user-structure <code>userParameters</code>
2. 16 byte randomly-generated value (<code>G$RADIUSCHAPKEY</code>) also from <code>userParameters</code>
3. Global LSA secret (<code>G$MSRADIUSCHAPKEY</code>)
4. Static key hardcoded in the Remote Access Subauthentication DLL (<code>RASSFM.DLL</code>)

With this information, an adversary may be able to reproduce the encryption key and subsequently decrypt the encrypted password value.(Citation: how_pwd_rev_enc_1)(Citation: how_pwd_rev_enc_2)

An adversary may set this property at various scopes through Local Group Policy Editor, user properties, Fine-Grained Password Policy (FGPP), or via the ActiveDirectory [PowerShell](https://attack.mitre.org/techniques/T1059/001) module. For example, an adversary may implement and apply a FGPP to users or groups if the Domain Functional Level is set to "Windows Server 2008" or higher.(Citation: dump_pwd_dcsync) In PowerShell, an adversary may make associated changes to user settings using commands similar to <code>Set-ADUser -AllowReversiblePasswordEncryption $true</code>.

## 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

- Password Policies
- Privileged Account Management

## 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.