Observed Signal · Jul 15, 2026 · Technical Release · Source: DEV Community · Impact: 2/5 · Sentiment: Positive
Red‑teaming an LLM security gateway: four‑pass findings
The author describes building and red‑teaming a transparent OpenAI‑compatible LLM security gateway that inspects requests and responses for leaked secrets, PII, jailbreaks, prompt injection and exfiltration. Over four iterative passes (ingress evasion, harder request techniques, response/egress, and streaming egress) the author cataloged detection gaps, implemented fixes and validated benign‑guard tests to avoid false positives. Key fixes include Unicode tag‑character normalization, intent‑gated exfil rules, reuse of request‑side secret format rules on egress, an opt‑in RESPONSE_BLOCK mode that strips/blocks leaked content, and a rolling-window SSE streaming scanner that blocks fragmented streamed secrets. The article is explicit about remaining limitations (regex limits, streaming cannot retract already-streamed prefixes, domain‑list maintenance, and that this does not solve prompt injection architecture issues). The gateway repo is published under Apache‑2.0.
Practical, reproducible security hardening for LLM ingress/egress and streaming egress improves operational defenses for deployments, but it's an individual open‑source gateway and not an industry‑wide platform change.
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Key Takeaways & Evidence Grounding
- Author built an OpenAI‑compatible transparent proxy gateway that scans every LLM request and response for secrets, PII, jailbreaks, prompt injection, and exfiltration using deterministic pattern detection.
- The author ran four red‑team passes (request warmup, harder request techniques, response/egress, and streaming egress) and iteratively fixed detection gaps while validating benign‑guard tests.
- Notable fixes: normalization of Unicode tag characters, intent‑anchored exfil rules and destructive‑command gating, reuse of request‑side secret rules on responses, opt‑in RESPONSE_BLOCK to block leaked responses, and a rolling 500‑character window SSE streaming scanner to catch fragmented secrets.
- After fixes, request and response secret detection achieved parity and streaming enforcement withheld chunks that completed secrets; zero new false positives were introduced in tests.
- Repository published at github.com/akav-labs/agentsentry-gateway under Apache‑2.0.
Connected Companies & Entities
6 Entities mapped“It sits in front of the model as a transparent OpenAI-compatible proxy — one env var, `OPENAI_BASE_URL` — and scans every request (and respo...”
“It missed OpenAI project keys, Anthropic keys, Stripe keys, private-key blocks, every system-prompt-disclosure phrasing, every exfil link, a...”
“It missed OpenAI project keys, Anthropic keys, Stripe keys, private-key blocks, every system-prompt-disclosure phrasing, every exfil link, a...”
“Plus Twilio account SIDs, and PII _values_ (US SSN, credit-card numbers) — context-anchored so a git SHA or an order number doesn't look lik...”
“The AWS IMDS IP (`169.254.169.254`) was caught by accident (numeric-IP rule)....”
Ontology Mapping & Concepts
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