This syndicated post originally appeared at No Jitter - Recent posts by Zeus Kerravala.

Session border controllers can alleviate the main security
concerns specific to VoIP use and real-time communications.

With an unprecedented number of high-profile cyberattacks hitting several large banks and major retailers this year, interest in improving IT security of late has been hotter than Apple and Tesla put together. But in my conversations with security resellers, I’ve come to realize that the due diligence stops short of real-time communications.

When it comes to securing communications flows, firewalls just aren’t enough. Firewalls do a good job of preventing data loss and security applications but they aren’t made for the unique needs of real-time communications. To protect the communications infrastructure, businesses should leverage session border controllers (SBCs).

Whenever I talk to anyone about SBCs, topics like SIP trunking termination or network address translation come up because most companies deploy them for these purposes. However, SBCs can play a critical role in securing communications, particularly in regards to these five main concerns.

1. Protecting against malicious attacks. Denial-of-service (DOS) or distributed DOS (DDOS) attacks can flood the network with bad traffic. While DOS or DDOS attacks aren’t isolated to real-time traffic, the flood of traffic they unleash can seriously degrade the quality of voice and video. You can use SBC features like VLAN tagging to separate voice traffic from general traffic and mitigate the maliciousness of attacks. In addition, you can use an SBC’s built-in firewall to allow voice to pass through while dropping other traffic and minimizing the impact of DOS attacks.

2. Toll fraud protection. Toll fraud occurs when hackers break into a business VoIP system and make personal calls on the company’s dime. The amount of toll fraud has steadily increased over the past decade, leaving businesses around the world on the hook for billions of dollars in fraudulent toll charges. To stop toll fraud, you can configure your SBC to disable all sources of secondary dial tone.

3. Encryption. Both signaling and media traffic need to be encrypted to secure real-time communications. SIP messages are fairly easy to intercept as they use plain text for signaling. To secure the signaling traffic, SBCs use Transport Layer Security to secure the signaling traffic and make it invisible to hackers. To secure media packets and add another layer of protection, SBCs use the Secure Real-time Protocol. The SBC can provide other forms of encryption as well, providing protection from eavesdropping and protecting callers on a network. One note here, however: Encryption creates a significant drain on the SBC. If you’re using a hardware-based SBC appliance, be sure to add separate hardware for the encryption. If you’re using a virtual SBC appliance, make sure you test it before rolling it out into a production environment.

4. Topology hiding. When VoIP messages pass between two networks, the payload can provide the recipient the ability to understand the topology of the networks as well as the route taken. The SBC protects against this through a feature called topology hiding, which manipulates the IP addresses and header information as the calls pass through it.

5. IP traffic management. This security feature, also known as call admission control, limits the number of simultaneous sessions active at any one time. IP traffic management is enabled on a per-SBC basis and monitors the total number of simultaneous inbound and outbound calls. This is similar to DOS protection and ensures that massive call volume doesn’t degrade the performance of other calls.

Other issues, such as failure recovery and high-availability planning, have security implications you’ll want to consider, as well. You can address most of those with good network design, although the SBC will still play a crucial role.

The issues I listed above are the main security concerns specific to VoIP deployments. While some network firewall vendors may claim to address some of these issues, they’re just not meant to handle real-time communications. For this, businesses should turn to SBCs.

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Zeus Kerravala

Zeus Kerravala is the founder and principal analyst with ZK Research. Kerravala provides a mix of tactical advice to help his clients in the current business climate and long term strategic advice.
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