Shipped surface
Open Voice Shield takes your SIP traffic as an ordinary hop, relays and records the media, and routes the call on to your own destination. After hangup it transcribes and scores the conversation, producing a fraud verdict with its evidence. Everything on this page is in production today, with one exception: Voice AI forwarding is labelled beta wherever it appears.
The groups below follow the order a call meets them. Integration detail is on how it works; the controls behind it are on security.
Group 1 — the call path
OVS is a SIP proxy with a media server anchoring the media, so it is in the media path. That is how the call gets recorded. It is not a B2BUA: the dialog is proxied, record-routed and relayed on.
Every INVITE is authorized by source IP against a per-tenant CIDR allow-list. No digest auth, no registration: REGISTER is answered 403. An unlisted source, a suspended account, an exhausted balance and a port limit each get their own SIP response code.
Routing rules match a leading prefix of the dialed number, longest match first, priority as tie-break. Each rule points at one of your destinations, which may carry a tech_prefix prepended to the Request-URI user before relay. With no rule: the whitelisted IP's destination, then the account default, then the source IP.
Named headers on the initial INVITE are captured onto the call. X-Customer-ID and X-Customer-Name ship configured, in indexed CDR columns you can filter by. Other configured headers go to a JSON map on the call, the webhook payload and the alert e-mail.
The authorization response carries a max_call_seconds computed from the prepaid balance. The proxy enforces it from the 200 OK and BYEs both sides on expiry, so a call cannot outrun the money that pays for it. Re-INVITEs cannot extend it.
Every ringing and answered call, live: ANI, dialed number, customer reference, routing, elapsed time, remaining credit. A port-bank faceplate shows one LED per licensed port. Administrators see all tenants, with a per-customer summary.
A destination can be a voice AI agent reached as a SIP endpoint over TLS, so a screened call goes to an agent instead of a human queue. Beta: exercised only against a test agent, no certificate verification on the TLS client profile, and one shared digest credential rather than one per destination.
Group 2 — the verdict
Analysis begins after the BYE, never during the call. Nothing is injected into the live audio: no prompt, no tone, no added delay.
| Stage | What happens | Result on the call |
|---|---|---|
| Capture | The media server writes one pcap per media stream while it relays the RTP. | pcap on the media node |
| Decode | The pcap is parsed, RTP grouped by SSRC, G.711 PCMU/PCMA decoded to PCM, gaps filled from RTP timestamps. | stereo 8 kHz WAV |
| Transcribe | Each channel is transcribed separately, then merged by start time, so every line is attributed to caller or callee. | speaker-labelled transcript |
| Analyze | The analysis engine reads the transcript and call metadata, returning a strict JSON verdict. | analysis record |
| Notify | Matching alert rules e-mail the analysis. A configured webhook is POSTed, HMAC-signed. | alert + webhook delivery |
Two honest limits
Calls shorter than the configured minimum are marked skipped, not analyzed. Codecs other than G.711 — G.722, Opus, dynamic payload types — are not decoded today. Such a call is relayed and billed normally, but records unsupported_codec instead of a transcript.
Each call records whether its speech-to-text and analysis stages ran on the server or against a cloud API. We publish no accuracy figure: none has been measured against a labelled corpus. What has been measured is on the benchmark page.
Group 3 — the response
The enforcement surface is the next call from that number, not the current one. The analysis exists only after the call has ended.
A rule reads like a sentence: when probability is at or above a threshold and the recommendation is one you chose, block that calling number or divert it, for a window you set or permanently. The control applies at authorization, before routing, so a blocked ANI gets SIP 403 and shows in the CDR as blocked_by_rule. A controlled-numbers table lists every active control with its reason and expiry; one action releases it.
Rules match on minimum probability, category and recommendation, deliver to up to ten addresses, throttle repeats and can attach the transcript. Every account is seeded with one enabled rule — probability 90 or above with a block recommendation — so the first dangerous call reaches you with nothing configured. Every attempt is recorded as sent, failed or skipped.
Open a case from the call detail, title pre-filled from the analysis. Set severity, assign it to a user on your account, and work it through open, in review, resolved or dismissed with a comment thread. Creation, assignment and comments e-mail the people involved.
A completed analysis is POSTed to your endpoint, signed HMAC-SHA256 in X-OVS-Signature, with an X-OVS-Delivery id for idempotency. The payload carries call metadata, captured headers and the analysis, so you can drive your own switch from it.
Group 4 — the evidence
A fraud verdict is only useful if you can prove it. Every call keeps its raw material; three routes get it out.
| Artefact | Contents | How you get it |
|---|---|---|
| Recording | Stereo WAV, caller on one channel and callee on the other | Player in the call detail, or streamed download |
| SIP ladder | The traced SIP messages of that call, timestamped with direction | Diagnostics card, plus a .txt download |
| Media pcap | The media capture(s), zipped when the call had several legs | GET /calls/<id>/pcap |
| Analyst bundle | Self-contained HTML report, JSON, transcript, WAV, SIP log and pcaps | One .zip from the call's action menu |
| Shared link | Read-only verdict, red flags, transcript and audio — nothing else | A URL and a generated password |
One action produces a single .zip that opens days later with no account, no network and no tooling. The report inside is self-contained — inline CSS, no scripts, no web fonts, no remote images — and prints cleanly. Anything retention has already deleted is listed as a noted omission, not silently missing.
Share one call with a client, a carrier or an investigator without giving them an account. The platform generates the password — twelve characters, grouped for reading aloud, no ambiguous glyphs — and shows it once. A link expires in 24 hours, 7 days, 30 days or never, can be revoked or rotated, and records how often it was opened. The shared page omits routing internals, the SIP log and the pcap.
Group 5 — the account
Up to ten users on an account, as owners or members. Owners invite, deactivate and reactivate. An invited user gets a temporary password by e-mail and must change it at first sign-in. The audit log records the acting user, not just the account.
WebAuthn passkeys as an optional second factor. Register one or more, name them, see when each was last used, remove them. Removing the last turns two-factor off.
Every screen in the portal is a documented REST endpoint. Keys are bound to the user who minted them, revocable, and dead the moment that user is deactivated. The API reference is on this same origin.
Recordings and captures stay on the operator's disk, or move to an operator-controlled S3 bucket after a configurable number of hours. Playback, download and export work the same either way.
Independent retention windows for recordings, pcaps and SIP logs; zero means keep them. Expiry deletes the object, local or in the bucket. The call record keeps its metadata.
A scheduled gzipped database dump, written to a bucket or local disk at a time you set, keeping the last N. Backups list size and date, can be taken on demand, downloaded, and restored behind a typed confirmation.
Group 6 — the money
Billing is prepaid. A call is charged for its minutes, and its first analysis is charged a flat per-call fee. A re-analysis is never charged.
| Mechanic | Behaviour |
|---|---|
| Usage | Per-minute rate with a plan-specific minimum billable duration, then per second. |
| Analysis fee | A flat charge when a call's first analysis completes; re-runs are free. |
| Bundles | A monthly plan with included minutes and concurrent ports. Overage at the plan rate. |
| Balance gate | An empty balance refuses the next call at authorization with SIP 402, and caps the current one. |
| Pilot | A time-boxed, optionally minute-capped free period. Ledger lines show $0.00 with the waived amount beside them. Billing resumes when it ends, never retroactively. |
| Ledger | Every charge, fee, top-up and adjustment is a line you can read and export. |
On the operator side, each call carries its own commercial line, with running totals for whatever filter the CDR is showing.
Whitelist your SIP server's IP, point a trunk at the ingress, place one call. The verdict is in the console when the call ends.