VoIP security

Protect distinct surfaces

A PBX has administration, signaling and media surfaces, plus dependencies such as backups and provisioning. A phone's permission to make a call should not grant access to the management interface. Separate network access and credentials by role.

Limit the cost of a compromised account

Give extensions only the calling permissions their users need. Restrict high-cost destinations where inappropriate, and arrange carrier usage notifications or limits where supported. A strong password alone does not make an unrestricted outbound route a sound design.

Keep administrative interfaces behind a restricted access path. Review vendor security guidance and maintenance status. Encryption addresses confidentiality and integrity on configured paths; it does not replace access policy, patching or destination controls.

Make recovery possible

Protect backups as sensitive data, store them away from the PBX and document who can restore them. Test restores in isolation to avoid duplicate registrations and chargeable calls. Keep an incident contact path outside the phone system itself.

For suspected compromise, preserve useful evidence, constrain affected access and work with the carrier on anomalous calling. Rebuild confidence in the system before restoring broad access. Do not disable security controls merely to make a diagnostic test pass.

Preserve Linphone downgrade and peer-verification evidence

Liblinphone documents different outcomes for mandatory and optional media encryption, while ZRTP adds a separate peer-authentication token. The Linphone guide and diagnostic keep a policy failure, negotiated protection and SAS verification as distinct evidence.

Verify IP Telecom optional TLS and SRTP on every hop

IP Telecom says encrypted signaling and media can be offered where the PBX supports them. The provider record requires account enablement, certificate and trust evidence, cipher selection, SRTP keying and intermediary boundaries before making a protection claim.

Require a negotiated Clearfly protection profile

The reviewed Clearfly pages do not define one TLS or SRTP profile. The provider record keeps certificate validation, protocol, cipher, media keying, downgrade policy and unprotected intermediary legs as account-specific acceptance evidence.

Allow-list dynamic dialplan targets

The Asterisk lookup guide treats context, extension, priority and subroutine arguments as bounded control data rather than raw caller input.

Require the selected Redcentric protection profile

Current public Redcentric pages do not define one trunk-wide TLS or SRTP profile. The provider record keeps certificate validation, protocol, cipher, media keying, downgrade policy and intermediary legs order specific.

Prove CommPeak TLS and SRTP on every ordered leg

CommPeak instructs third-party clients to enable SRTP manually when using TLS. The provider record requires transport, certificate, cipher, media keying, downgrade behavior and intermediary-leg evidence rather than assuming encryption from a product claim.

Restrict the Asterisk metrics exposure

The Prometheus metrics guide combines Basic authentication with network restriction, secret custody and protected transport instead of treating a successful scrape as a safe design.

Constrain database-backed dialplan functions

The func_odbc guide combines validated arguments, documented escaping, a least-privilege database account and a supported maintenance release.

Authorize and constrain every database mutation

The ODBC writes and transactions guide combines a fixed function, validated inputs, least-privilege account, affected-row checks and database-enforced invariants.

Scope Voximplant protection to each signaling and media leg

Voximplant publishes TLS, SDES, DTLS and optional IPsec capabilities. The provider record still requires certificate, trust, keying, downgrade and intermediary-leg evidence for the ordered path.

Treat CORS, authentication and firewalls as different controls

The Asterisk HTTP service guide keeps browser-origin policy, service credentials, per-user ACLs and network reachability separately observable.

Treat security-event records as evidence, not automatic verdicts

The Asterisk security-event guide separates typed events, logger output, alerting and enforcement rather than declaring every record an attack.