Nemesis Shield — Ruby

Native Ruby SDK for Nemesis Shield. Learns your app's normal behavior; in enforce mode BLOCKS off-baseline requests (auth bypass, path traversal, scanners, unusual methods) before your app runs. One Rack middleware works with Rails, Sinatra and any Rack app. Positive-security, fail-open, privacy-preserving.

Rails — config/application.rb:

require "nemesis_shield"
config.middleware.use NemesisShield::Middleware, token: ENV["NEMESIS_TOKEN"]

Sinatra:

require "nemesis_shield"
use NemesisShield::Middleware, token: ENV["NEMESIS_TOKEN"]

Rack (config.ru):

require "nemesis_shield"
use NemesisShield::Middleware, token: ENV["NEMESIS_TOKEN"]
run MyApp

Observe (default) → learn & approve behaviors in the console → flip to enforce (the SDK polls the policy in the background, no redeploy) → off-baseline requests get 403 blocked_by_nemesis_shield. Verified end-to-end (learn → enforce → attack) on Rails, Sinatra and Rack: legit passes (200); attacks blocked (403).

LLM Guard (OWASP LLM Top 10)

The same HashLR ML classifier every Nemesis Shield SDK ships — catches obfuscated/paraphrased prompt injection signature rules miss, scored identically in every language.

require "nemesis_shield_llm"

v = NemesisShield::LLM.guard_llm(user_prompt, enforce: true)
refuse! if v[:blocked]   # v[:kind], v[:score], v[:owasp] ("LLM01")

score = NemesisShield::LLM.ml_injection_score(user_prompt) # 0..1

Regex first, then ML. Blocks at ≥ 0.85 (high), flags at ≥ 0.45.

Full coverage & safe-unlock

Mount it first / outermost so every route is inspected (not just API routes — attackers hit any path):

use NemesisShield::Middleware, token: ENV["NEMESIS_TOKEN"]   # top of the Rack stack

What's inspected (privacy-preserving): method + normalized route + query-param structure (names + kinds, never values) + auth flag + status. An off-baseline route, param structure, method, or auth state is blocked in enforce mode. Path-traversal segments normalize to {traversal}.

Safe-unlock (break-glass): the login/auth path is never blocked, so a still-learning baseline can't lock you out. Defaults: /login /signin /sign-in /auth /oauth /session /wp-login.php /wp-admin. Override:

export NEMESIS_SHIELD_BOOTSTRAP="/login,/admin,/healthz"

Verify coverage — in observe mode, hit a normal route, a param, and a scanner path, then confirm all three appear in the console (Activity / Behaviors):

curl -s "http://localhost:8080/" >/dev/null
curl -s "http://localhost:8080/search?q=shoes" >/dev/null
curl -s "http://localhost:8080/.env" >/dev/null   # shows up as an off-baseline behavior