# Backend Inferencer > Infers backend technologies including servers, languages, frameworks, databases, and CMS - Skill: `uhdyindy/backend-inferencer` (Agent Skill) - Install (CLI): `npx skillmds@latest add uhdyindy/backend-inferencer` - Raw SKILL.md: https://api.skillmd.com/api/skills/uhdyindy/backend-inferencer/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: UhdyIndy (https://skillmd.com/u/uhdyindy) - Updated: 2026-09-22 - Page: https://skillmd.com/skills/uhdyindy/backend-inferencer --- # Backend Inferencer Skill ## Purpose Infer backend technologies by analyzing HTTP headers, cookies, error pages, DNS records, and repository data. ## Input Raw signals from Phase 2: - `http_signals` - Server headers, X-Powered-By, cookies - `dns_signals` - Service verification TXT records - `repository_signals` - Dependencies, Dockerfiles - `html_signals` - Generator meta tags, CMS patterns ## Technology Categories ### Web Servers | Technology | Detection Signals | Weight | |------------|-------------------|--------| | nginx | Server: nginx, nginx error pages | 35-40 | | Apache | Server: Apache, Apache error pages | 35-40 | | Microsoft IIS | Server: Microsoft-IIS | 40 | | Caddy | Server: Caddy | 35 | | LiteSpeed | Server: LiteSpeed | 35 | ### Programming Languages | Technology | Detection Signals | Weight | |------------|-------------------|--------| | Node.js | X-Powered-By: Express, connect.sid cookie | 30-40 | | Python | X-Powered-By: gunicorn/Werkzeug, django_session cookie | 30-40 | | PHP | X-Powered-By: PHP, PHPSESSID cookie | 35-40 | | Ruby | _rails_session cookie, X-Request-Id | 30-40 | | Java | JSESSIONID cookie, X-Powered-By: Servlet | 35-40 | | Go | Custom patterns, repo analysis | 25-35 | | .NET | ASP.NET_SessionId cookie, X-AspNet-Version | 40 | ### Backend Frameworks | Technology | Detection Signals | Implies | Weight | |------------|-------------------|---------|--------| | Express.js | X-Powered-By: Express | Node.js | 40 | | NestJS | Nest patterns, repo analysis | Node.js, TypeScript | 35 | | Fastify | Fastify patterns | Node.js | 35 | | Django | csrftoken/django_session cookies | Python | 40 | | Flask | Werkzeug server | Python | 35 | | FastAPI | uvicorn patterns | Python | 35 | | Rails | _rails_session cookie | Ruby | 40 | | Laravel | laravel_session cookie, XSRF-TOKEN | PHP | 40 | | Symfony | symfony cookie patterns | PHP | 35 | | Spring | JSESSIONID, X-Application-Context | Java | 35 | | ASP.NET | ASP.NET_SessionId | .NET | 40 | ### Content Management Systems | Technology | Detection Signals | Weight | |------------|-------------------|--------| | WordPress | /wp-content/, /wp-admin/, generator meta | 45 | | Drupal | X-Drupal-Cache, /sites/default/ | 45 | | Joomla | generator meta, /components/ | 40 | | Magento | /skin/frontend/, Mage patterns | 40 | | Shopify | myshopify.com, Shopify patterns | 45 | | Contentful | Contentful API patterns | 35 | | Strapi | Strapi patterns | 35 | | Ghost | Ghost generator meta | 40 | ### Databases (Indirect Signals) | Technology | Detection Signals | Weight | |------------|-------------------|--------| | PostgreSQL | pg dependency, Heroku Postgres | 25-30 | | MySQL | mysql dependency, common patterns | 25-30 | | MongoDB | mongoose dependency, MongoDB Atlas TXT | 30 | | Redis | redis dependency, session patterns | 25-30 | | Elasticsearch | elasticsearch dependency | 25-30 | | DynamoDB | AWS SDK patterns, boto3 | 25-30 | ### API Technologies | Technology | Detection Signals | Weight | |------------|-------------------|--------| | GraphQL | /graphql endpoint, schema patterns | 35 | | REST | /api/v1, OpenAPI spec | 25 | | gRPC | grpc patterns in repos | 30 | | tRPC | tRPC patterns | 30 | ## Inference Logic ```python def infer_backend_technologies(signals): results = [] # Web Server Detection server_header = signals.http_signals.get('Server', '') for server in SERVER_PATTERNS: if server.pattern.match(server_header): results.append({ "name": server.name, "category": "Web Server", "version": extract_version(server_header, server.pattern), "signals": [{"type": "http_header", "value": f"Server: {server_header}"}], "total_weight": server.weight }) # Language/Framework from X-Powered-By powered_by = signals.http_signals.get('X-Powered-By', '') for framework in POWERED_BY_PATTERNS: if framework.pattern in powered_by: results.append({ "name": framework.name, "category": framework.category, "implies": framework.implies, "signals": [{"type": "http_header", "value": f"X-Powered-By: {powered_by}"}], "total_weight": framework.weight }) # Cookie-based Detection for cookie in signals.http_signals.cookies: for pattern in COOKIE_PATTERNS: if pattern.name in cookie: results.append({ "name": pattern.tech, "category": pattern.category, "implies": pattern.implies, "signals": [{"type": "cookie", "value": f"Cookie: {cookie}"}], "total_weight": pattern.weight }) # CMS Detection from HTML for cms in CMS_PATTERNS: score = 0 evidence = [] if cms.generator_pattern in signals.html_signals.generators: score += 40 evidence.append("Generator meta tag") for url_pattern in cms.url_patterns: if url_pattern in signals.html_signals.script_urls: score += 20 evidence.append(f"URL pattern: {url_pattern}") if score > 0: results.append({ "name": cms.name, "category": "CMS", "signals": evidence, "total_weight": score }) # Repository-based Detection if signals.repository_signals: for dep_file, deps in signals.repository_signals.dependencies.items(): for dep in deps: if dep.name in DEPENDENCY_PATTERNS: pattern = DEPENDENCY_PATTERNS[dep.name] results.append({ "name": pattern.tech, "category": pattern.category, "version": dep.version, "signals": [{"type": "dependency", "value": f"{dep.name}@{dep.version}"}], "total_weight": pattern.weight }) return results ``` ## Output ```json { "skill": "backend_inferencer", "results": { "technologies": [ { "name": "nginx", "category": "Web Server", "version": "1.18.0", "signals": [ { "type": "http_header", "value": "Server: nginx/1.18.0", "source": "https://example.com", "weight": 40 } ], "total_weight": 40 }, { "name": "Express.js", "category": "Backend Framework", "signals": [ { "type": "http_header", "value": "X-Powered-By: Express", "source": "https://api.example.com", "weight": 40 }, { "type": "cookie", "value": "connect.sid session cookie", "source": "https://example.com", "weight": 30 } ], "total_weight": 70, "implies": ["Node.js"] }, { "name": "Node.js", "category": "Runtime", "signals": [ { "type": "implied", "value": "Implied by Express.js detection", "weight": 0 }, { "type": "dependency", "value": "node version in package.json", "source": "github.com/example/repo", "weight": 35 } ], "total_weight": 35 }, { "name": "PostgreSQL", "category": "Database", "signals": [ { "type": "dependency", "value": "pg@8.11.0 in package.json", "source": "github.com/example/repo", "weight": 30 } ], "total_weight": 30 } ], "implied_technologies": [ { "name": "Node.js", "implied_by": ["Express.js"], "confidence": "High" } ], "summary": { "web_server": "nginx", "runtime": "Node.js", "framework": "Express.js", "database": "PostgreSQL", "cms": null } } } ``` ## Version Detection ### From Headers ``` Server: nginx/1.18.0 → nginx 1.18.0 X-Powered-By: PHP/8.1.0 → PHP 8.1.0 X-AspNet-Version: 4.0.30319 → ASP.NET 4.x ``` ### From Dependencies ```json // package.json "express": "^4.18.2" → Express.js 4.18.x // requirements.txt Django==4.2.1 → Django 4.2.1 // Gemfile gem 'rails', '~> 7.0' → Rails 7.0.x ``` ## Error Handling - Missing headers: Continue with other signals - Ambiguous cookies: Include all possibilities - Conflicting signals: Report both, flag for correlation phase