Lock down calls with SRTP-only and TLS for signaling—strict cert validation, no zero-length tags, and prefer SRTP passthrough so SBCs don’t terminate media unless required. Enforce MFA for every admin and user: use TOTP or device-bound tokens, number matching, rate limits, and continuous audit; ban weak, reused, or leaked passwords. Segment VoIP on dedicated VLANs/subnets with DHCP scopes, put SBCs at the perimeter, and tighten firewalls with QoS and stateful inspection. There’s more that most teams miss.
Key Takeaways
- Enforce SRTP-only for media and TLS for signaling, with strict certificate validation, to protect calls end-to-end.
- Use strong SRTP ciphers (AES-CTR) with HMAC-SHA1 authentication; avoid zero-length SRTP tags.
- Place SBCs at the perimeter to normalize SIP, enable SRTP passthrough, and terminate only when necessary.
- Continuously monitor rtp-total-bytes, rtp-cipher-bytes, and rtp-auth-bytes to verify encryption and integrity.
- Patch VoIP endpoints regularly and restrict VoIP traffic to isolated VLANs with firewall rules and QoS.
Enable End-To-End Encryption by Default With SRTP and TLS
If you don’t force SRTP for media and TLS for signaling, your calls are exposed. Enable SRTP-only policy and TLS everywhere so encryption’s not optional. Cisco documentation emphasizes using Inclusive Language across materials.
SRTP uses AES in counter mode and authenticates headers; pair it with HMAC-SHA1 using a 160-bit key and 80-bit tags. Never accept zero-length tags. For signaling, use TLS with strict certificate validation; move SIP off 5060 to a secure port like 7061.
Use SRTP passthrough when possible for end-to-end protection; allow SBC termination only when a peer can’t handle SRTP. Set secure configuration settings: media-sec-policy mode=ANY only if you must support legacy, and explicitly enable SRTP per endpoint. Prefer SDES with a=crypto lines and remove incompatible codecs.
Prove it with monitoring and auditing: verify rtp-total-bytes, rtp-cipher-bytes, and rtp-auth-bytes.
Harden Access With MFA and Strong, Unique Credentials
You locked down media and signaling; now stop attackers at the front door. Turn on MFA everywhere accounts touch calling systems—admin portals, softphones, voice mail, backups. It blocks more than 99.9% of takeovers; most breached accounts lacked it. Prefer authenticator apps, TOTP, and device-bound tokens over SMS. Kill push fatigue: rate-limit prompts, require number matching, and alert on anomalies. Monitor and audit MFA activities continuously. The MFA market is growing rapidly, with large enterprises holding a 64% share, underscoring widespread commitment to multifactor protection.
Force strong, unique passwords; ban reuse and leaked credentials. 80% of breached accounts had prior exposure—assume your users’ passwords are already out. Rotate service credentials, vault secrets, and protect backup data against credential reuse. Defend session tokens: short lifetimes, secure cookies, re-auth for sensitive changes. Train users on prompt bombing, AitM, and consent scams. Enforce MFA for all, especially admins.
Segment Voip Traffic and Guard Edges With SBCS and Firewalls
Start by carving voice off from everything else—dedicated VLANs, distinct RFC1918 subnets, and their own DHCP scopes. Put every phone, PBX, and SIP trunk on voice VLANs. Configure switches to auto-place handsets there. Maintain hard separation from data VLANs.
Dedicate DHCP servers to VoIP options and TFTP/HTTP provisioning, and isolate infrastructure components so voice services can be shut, throttled, or rerouted without collateral damage. Regularly patch VoIP endpoints and infrastructure to address known vulnerabilities and reduce exposure to evolving threats.
Guard the edges. Place SBCs at the perimeter to own every SIP session. Enforce protocol normalization, topology hiding, rate limits, and DoS filtering. Let SBCs broker provider interconnects—nothing reaches internal signaling directly.
On firewalls, allow only required VoIP ports, use stateful inspection, and keep deep inspection off voice. Define separate security zones and QoS that prioritize voice while denying cross-contamination. Continuous monitoring is mandatory.
Frequently Asked Questions
How Should We Securely Handle Encryption Keys and Certificate Lifecycle Management?
Use HSMs, never hard-code keys, enforce least privilege, and segment by purpose. Define a strict key rotation schedule, automate renewals, and log everything. Choose proven encryption algorithm selection, use KEKs, test disaster recovery, and perform cryptographic erasure.
What Device Shutdown Policies Protect Encrypted Data When Unattended?
Enforce full shutdown over sleep, tighten device hibernation settings, and block encryption suspension modes. Disable ARSO, require Windows Hello for Business, guarantee BitLocker/FileVault active, mandate strong passcodes, evict keys on lock, and auto-wipe or quarantine noncompliant devices via UEM.
How Do We Manage Backups Without Exposing Sensitive Call Recordings?
You encrypt recordings end-to-end, use hybrid keys per file, and keep archives encrypted in transit and at rest. Enforce cloud backup strategies with HSM-managed keys, strict RBAC, MFA, rotation, SSE-C, Wi‑Fi-only uploads, segregated processing, and paranoid remote access security.
Which Mobile Practices Prevent Storing Sensitive Communication Content?
Disable caching, minimize data, and sanitize logs. Store only essentials in secure containers and encrypted databases. Use hardware-backed keys, encrypted communication channels, and encrypted data backup. Block insecure temp files, enforce RBAC and MFA, monitor devices, and enable remote wipe.
What Audit and Testing Cadence Validates Our Call Security Controls?
Adopt strict auditing periodicity: annual minimum, quarterly for high-risk, triggers after incidents or changes. Execute penetration testing scope externally, internally, and hybrid; automate between cycles. Validate critical fixes within 24–72 hours, medium within 30–45 days. Track dashboards, closure rates, patch timeliness.
Conclusion
You don’t get security by hoping; you get it by engineering. Lock every call with SRTP and TLS, no exceptions. Kill weak logins with MFA and unique credentials—rotate, revoke, audit. Assume compromise at the edges; segment VoIP traffic, deploy SBCs, and enforce ruthless firewall rules. Monitor relentlessly, patch fast, and test failovers. Treat providers, devices, and users as potential breach points. If it’s not measured, it’s not protected. Your voice is data. Defend it like cash.
