Abnormal Security

abnormal-mcp

MCP server for Abnormal Security — AI-powered threat detection, case management, and email remediation.

Tools

This server uses a decision-tree architecture. Start by calling abnormal_navigate to select a domain, then use the domain-specific tools.

Navigation

Tool	Description
abnormal_navigate	Navigate to a domain (threats, messages, remediation, abuse, cases)
abnormal_back	Return to domain selection

Threats domain

Tool	Description
abnormal_threats_list	List detected threat cases (paginated)
abnormal_threats_get	Get full details of a specific threat by ID

Messages domain

Tool	Description
abnormal_messages_list	List messages within a threat case
abnormal_messages_get	Get detailed message analysis (headers, URLs, attachments, AI analysis)

Remediation domain

Tool	Description
abnormal_remediation_manage	Trigger or check remediation actions for a message

Abuse domain

Tool	Description
abnormal_abuse_list	List phishing emails reported via the Abuse Mailbox

Cases domain

Tool	Description
abnormal_cases_list	List active security investigation cases
abnormal_cases_get	Get details of a specific case

Interactive Threat Card (MCP Apps)

• abnormal_threats_get renders as an interactive threat card in MCP Apps hosts (Claude Desktop/web): subject, sender, attack classification, remediation status, and the messages in the threat. The card is read-only — remediation stays a deliberate, model-mediated action. Plain-JSON behavior is unchanged in other hosts. Neutral by default, brandable via window.__BRAND__ injection or MCP_BRAND_* env vars (MCP_BRAND_NAME, MCP_BRAND_LOGO_URL, MCP_BRAND_PRIMARY_COLOR, MCP_BRAND_ACCENT_COLOR, MCP_BRAND_BG, MCP_BRAND_TEXT) — no rebuild needed.

Authentication

Abnormal Security uses Bearer token authentication. Copy .env.example and set the variables below.

Variable	Required	Description
ABNORMAL_API_TOKEN	For stdio and AUTH_MODE=env	Abnormal Security API token. Generate it in the Abnormal portal under Settings > Integrations > API.
MCP_TRANSPORT	No	stdio (default) or http
AUTH_MODE	No	env (default outside Docker) or gateway. The image and Compose service set gateway. Gateway mode requires Authorization: Bearer on each /mcp request and never falls back to ABNORMAL_API_TOKEN.
CONDUIT_S2S_SECRET	Yes for HTTP	Service-to-service secret. Generate one with openssl rand -hex 32. The HTTP server logs an error and exits non-zero when this is empty or a known placeholder (changeme, placeholder, your-s2s-secret, replace-with-a-real-secret, and similar example values). Compose will not start without it. Never commit a real value. The value is never logged.
MCP_ALLOW_INSECURE_DEV	No	Set to exactly 1 only for local development to start HTTP without CONDUIT_S2S_SECRET. The process logs a warning, does not enforce X-Gateway-S2S, and binds 127.0.0.1 only. A non-loopback MCP_HTTP_HOST (including 0.0.0.0) is ignored and the override is logged. A known placeholder secret is still refused.
MCP_HTTP_HOST	No	Bind address when MCP_TRANSPORT=http. Defaults to 127.0.0.1 when unset. A configured secret honors this value. The container image sets 0.0.0.0. With no secret, the insecure-dev bypass forces 127.0.0.1.
MCP_HTTP_PORT	No	HTTP port. Defaults to 8080.

/health stays unauthenticated and does not read credentials. The stdio transport does not use CONDUIT_S2S_SECRET.

X-Gateway-S2S signing

With MCP_TRANSPORT=http and a real CONDUIT_S2S_SECRET, every /mcp request must include X-Gateway-S2S. The header value is t=<unix seconds>,v1=<hex>, where the hex is HMAC-SHA256 of the literal string t=<unix seconds> keyed with CONDUIT_S2S_SECRET (64 lowercase hex characters). The timestamp must be within 300 seconds of the server clock. A missing or invalid header returns 401 before the Abnormal token is read.

TS=$(date +%s)
SIG=$(printf 't=%s' "$TS" | openssl dgst -sha256 -hmac "$CONDUIT_S2S_SECRET" -hex | awk '{print $NF}')
curl -sS http://127.0.0.1:8080/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -H "X-Gateway-S2S: t=${TS},v1=${SIG}" \
  -H "Authorization: Bearer $ABNORMAL_API_TOKEN" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/list"}'

In AUTH_MODE=gateway that Authorization header is required and is the only credential source. AUTH_MODE=env still requires a valid X-Gateway-S2S header, then uses ABNORMAL_API_TOKEN from the environment when the request does not carry Authorization.

Standalone (env mode)

export ABNORMAL_API_TOKEN=your-api-token
node dist/index.js

Gateway mode

When deployed behind the MCP gateway, set AUTH_MODE=gateway. The gateway signs each /mcp request with X-Gateway-S2S and injects Authorization: Bearer {token}. Requests missing that credential header are rejected with 401.

Running

stdio (for Claude Desktop)

npm install
npm run build
node dist/index.js

HTTP Streamable (for hosted/gateway deployment)

HTTP refuses to start until CONDUIT_S2S_SECRET is a real secret:

CONDUIT_S2S_SECRET="$CONDUIT_S2S_SECRET" MCP_TRANSPORT=http AUTH_MODE=gateway node dist/index.js

Local HTTP without a secret is development-only. It binds 127.0.0.1 only and logs a warning:

MCP_TRANSPORT=http MCP_ALLOW_INSECURE_DEV=1 npm run start:http

Docker

The image listens on 0.0.0.0 inside the container (MCP_HTTP_HOST) and defaults to AUTH_MODE=gateway. Publish the port on loopback and pass the S2S secret. In gateway mode the API token arrives on each request as Authorization; the image does not read ABNORMAL_API_TOKEN.

docker build -t abnormal-mcp .
docker run \
  -e CONDUIT_S2S_SECRET="$CONDUIT_S2S_SECRET" \
  -p 127.0.0.1:8080:8080 \
  abnormal-mcp

Compose refuses to start when CONDUIT_S2S_SECRET is unset, sets AUTH_MODE=gateway, does not inject ABNORMAL_API_TOKEN, and publishes 127.0.0.1:8080:8080:

CONDUIT_S2S_SECRET="$CONDUIT_S2S_SECRET" docker compose up

Single-tenant HTTP (AUTH_MODE=env) still requires the S2S secret, then uses ABNORMAL_API_TOKEN:

docker run \
  -e CONDUIT_S2S_SECRET="$CONDUIT_S2S_SECRET" \
  -e AUTH_MODE=env \
  -e ABNORMAL_API_TOKEN=your-api-token \
  -p 127.0.0.1:8080:8080 \
  abnormal-mcp

Development

npm install
npm run dev          # watch mode
npm test             # run tests
npm run typecheck    # TypeScript type check
npm run build:ui     # rebuild the MCP Apps card bundle (only needed when ui/ changes)

License

Apache-2.0