# Censys Api

> Censys API v2 reference. Host reconnaissance and certificate data.

- **Type:** Skill
- **Install:** `agentstack add skill-liberty91ltd-cti-skills-censys-api`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [Liberty91LTD](https://agentstack.voostack.com/s/liberty91ltd)
- **Installs:** 0
- **Category:** [Agent Skills](https://agentstack.voostack.com/c/agent-skills)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [Liberty91LTD](https://github.com/Liberty91LTD)
- **Source:** https://github.com/Liberty91LTD/cti-skills/tree/main/skills/censys-api
- **Website:** https://liberty91.com/cti-skills

## Install

```sh
agentstack add skill-liberty91ltd-cti-skills-censys-api
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# Censys API v2

## Base URL
`https://search.censys.io/api/v2`

## Authentication
Basic Auth: `$CENSYS_API_ID:$CENSYS_API_SECRET`

```bash
curl -s "https://search.censys.io/api/v2/hosts/{ip}" \
  -u "$CENSYS_API_ID:$CENSYS_API_SECRET"
```

## Rate Limits
- Free: 250 queries/month, 5 results/query
- Paid: Higher limits based on plan

**Important:** Free tier is very limited. Use selectively — prioritise high-value lookups.

## Key Endpoints

### View Host
```bash
curl -s "https://search.censys.io/api/v2/hosts/{ip}" \
  -u "$CENSYS_API_ID:$CENSYS_API_SECRET"
```
**Useful fields:**
- `result.services[]` — port, service_name, transport_protocol, banner
- `result.services[].tls.certificates` — TLS certificate chain
- `result.autonomous_system` — ASN info
- `result.location` — geographic location
- `result.operating_system` — OS detection
- `result.last_updated_at` — scan freshness

### Search Hosts
```bash
curl -s "https://search.censys.io/api/v2/hosts/search?q={query}" \
  -u "$CENSYS_API_ID:$CENSYS_API_SECRET"
```
**Search syntax:** `services.port: 443 AND services.tls.certificates.leaf_data.subject.common_name: example.com`

### View Certificate
```bash
curl -s "https://search.censys.io/api/v2/certificates/{fingerprint}" \
  -u "$CENSYS_API_ID:$CENSYS_API_SECRET"
```

## Common Search Queries
- `ip: {ip}` — specific host
- `services.tls.certificates.leaf_data.subject.common_name: {domain}` — hosts with cert for domain
- `services.http.response.body_hash: {hash}` — hosts serving same content
- `services.jarm.fingerprint: {jarm}` — hosts with same JARM fingerprint (C2 detection)
- `labels: {label}` — Censys-labeled hosts

## CTI Value
Censys excels at:
- Certificate transparency analysis (finding related infrastructure)
- JARM fingerprinting (identifying C2 frameworks)
- Service banner analysis
- Historical infrastructure changes

## Response Summary Format
```yaml
ip: 
services:
  - port: 
    service: 
    banner: 
certificates:
  - subject_cn: 
    issuer: 
    valid_from: 
    valid_to: 
autonomous_system:
  asn: 
  name: 
location:
  country: 
  city: 
last_updated: 
```

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [Liberty91LTD](https://github.com/Liberty91LTD)
- **Source:** [Liberty91LTD/cti-skills](https://github.com/Liberty91LTD/cti-skills)
- **License:** MIT
- **Homepage:** https://liberty91.com/cti-skills

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** yes
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-liberty91ltd-cti-skills-censys-api
- Seller: https://agentstack.voostack.com/s/liberty91ltd
- Browse the marketplace: https://agentstack.voostack.com/browse

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Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.