Arcis vs Aikido Zen
Aikido Zen is a runtime application self-protection (RASP) agent that hooks into the Node.js process. Arcis is plain middleware. Both block attacks at runtime, but they get there very differently.
TL;DR
Aikido Zen monkey-patches built-in Node modules at startup to intercept dangerous calls (file system, child process, database driver, etc.) and stop attacks where they happen. Arcis sits in your middleware chain, sanitizes input at the request boundary, and blocks attack patterns before your handlers run. Aikido catches more bypass cases that pattern matching misses; Arcis is lighter, simpler to reason about, and works the same way across Node, Python, and Go.
Where Aikido Zen wins
- Process-level interception. By monkey-patching
fs,child_process, MongoDB driver, etc., Aikido catches attacks at the sink, not at the source. A path-traversal payload that slipped past pattern matching still fails when it tries to read/etc/passwd. - Less reliance on input pattern matching. Pattern-based defenses can be bypassed with novel encodings; sink-based defenses care about what the dangerous call actually does, not how the input was framed.
- Specific RASP guarantees. Aikido provides hard guarantees on a fixed list of sink categories (NoSQL injection in MongoDB, command injection in spawn/exec, path traversal in fs.read*, SSRF in http.request, etc.).
Where Arcis wins
- Three SDKs at full parity. Aikido Zen is Node-first. Their Python agent is newer; their Go support is limited. Arcis runs the same protections in Node, Python, and Go from a shared spec.
- No agent injection. Aikido requires a startup-time agent that monkey-patches your Node built-ins. That carries operational risk if a future Node release changes internals or another tool patches the same modules. Arcis is plain middleware: no monkey-patching, no agent, no startup hook.
- Fully open source under MIT. Aikido Zen is open core: the agent is open, but the orchestrator and dashboard sit behind a paid plan. Arcis is MIT all the way down, with all signatures, rules, and patterns in public files.
- 20+ vectors, not just sink-based ones. Aikido's RASP model only catches attacks at sinks. Things like rate limiting, security headers, CORS, CSRF, bot detection, prompt injection, and supply chain scanning live outside the sink set. Arcis bundles all of those.
Capability matrix
Comparison reflects public state of both projects as of 2026-05-10.
| Capability | Aikido Zen | Arcis |
|---|---|---|
| License | Open core (agent is open, control plane is paid) | MIT, fully open |
| Architecture | RASP agent (monkey-patches Node built-ins) | Middleware (no patching) |
| Languages | Node (mature), Python (newer) | Node, Python, Go (full parity, shared spec) |
| Detection model | Sink-based (intercept dangerous calls) | Source-based (sanitize at the request boundary) |
| Bypass resistance | Higher on covered sinks | Higher on novel attack surfaces (no monkey-patch dependency) |
| Coverage scope | Sinks Aikido knows about | 20+ request-boundary vectors (XSS, SQL, NoSQL, path, command, SSTI, XXE, SSRF, prompt injection, etc.) |
| Bot detection | Yes | Yes (635 patterns + behavioral signals) |
| Rate limiting | Yes | Yes (3 algorithms, optional Redis) |
| Security headers | No | Yes (16 headers) |
| CSRF protection | Yes | Yes (double-submit + HMAC) |
| Prompt injection | Roadmap | Yes (28 signatures, 3 severity tiers) |
| LLM token budget | No | Yes (sliding-window per-key cap) |
| Supply chain scanner | Yes (Aikido's broader product) | Yes (arcis sca) |
| Static analysis | Yes (Aikido's broader product) | Yes (arcis audit + arcis scan) |
| Operational footprint | Agent at process startup | One app.use(arcis()) |
How to choose
Pick Aikido Zen if:
- You want hard sink-level guarantees on the specific vectors Aikido covers (file system access, command execution, NoSQL operators in MongoDB, etc.).
- You're already on the broader Aikido platform (their wider product covers static analysis, secret scanning, dependency scanning, etc.) and want a unified vendor.
- Monkey-patching Node built-ins is acceptable in your environment.
Pick Arcis if:
- You run Python or Go services and want the same protections as your Node services.
- You want every signature, rule, and pattern in your security stack to be open and auditable under MIT.
- You don't want a startup-time agent or monkey-patches in your process.
- You want a broader request-boundary toolkit (rate limits, headers, CSRF, bot detection, prompt injection, supply-chain scanning) in one package.
Bottom line
Aikido Zen is a deeper Node-only RASP. Arcis is broader middleware that stays out of your runtime internals. Both have a place; the choice is whether you want sink-level intervention with an agent in your process, or boundary-level filtering with no patching.