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Is VoIP Secure? 5 Threats to VoIP Service and How to Mitigate Them
May 18th, 2016

Is VoIP Secure? 5 Threats to VoIP Service and How to Mitigate Them

Chris Turner

Just like your old phone lines could have been tapped, a Voice over Internet Protocol (VoIP) phone system has its own security risks. Because VoIP runs over the Internet using your existing data netwo...

Just like your old phone lines could have been tapped, a Voice over Internet Protocol (VoIP) phone system has its own security risks. Because VoIP runs over the Internet using your existing data network, VoIP is subject to the same security threats as your computers are. Fortunately, unlike the old phone systems, VoIP data can be encrypted enabling you to protect your system from being infiltrated and your data from breached. Solutions to guarantee the reliability of VoIP despite any threats are similar to the strategies you use to secure your computers and internal networks.

1. Intercepted data

A common threat with VoIP is a hacker hijacking unencrypted data and then listening to the conversations taking place. To do that, a cybercriminal must find the data source stream, which is easier if a company does not use a secure wireless network – a rare occurrence nowadays. If your business still has an unsecured wireless network, you should prioritize correcting the problem to protect VoIP and other data from being hacked. Your network also is vulnerable at the physical access point (a LAN hub), but here too, enterprises more frequently use Ethernet switches, which reduces the number of points where the system may be exploited.

To protect against someone being able to listen to hijacked data, you should ensure to encrypt VoIP data packets. Data encryption can be enacted at different levels. Application layer encryption can be utilized to get end-to-end protection. You also should ensure network layer encryption by operating over a Virtual Private Network (VPN).

2. Denial of Service (DoS)

A DoS attack is engineered by overloading a network with immense volumes of data, forcing the network to stop operating properly or collapsing entirely. If a DoS attack is launched from thousands of computers at once, it is much more troublesome. This type of attack is called a DDoS and can cause issues with phone call clarity as well as dropped lines.

Hackers typically target the main network when trying to disrupt the commercial activities of a business, so you can avoid system interruption if you use a cloud-based Public Branch Exchange (PBX) for your VoIP system. This will take your VoIP phone off your internal network and onto the network of your service provider, protecting your communication system in case of an attack on your main network. Firewalls, which should already be a part of a well-secured digital network, also help mitigate the risks of DDoS attacks.

3. Data extraction

A significant concern for companies is the extraction of private information from their digital networks. This threat is not new to VoIP, so you likely are already protecting your network against this threat with enhanced firewalls. However, an attack via a VoIP data packet will not be blocked by a firewall because it will not identify the VoIP data packet as an attack. It is more complex to scrutinize a VoIP data packet for secret malicious content. Extra scanning can delay data transmission, which will directly impact phone call quality. VoIP trojans typically transmit stolen data from the hacked system via a real-time transport protocol (RTP) stream.

An effective countermeasure to alleviate the risk of data extraction is Deep Packet Inspection (DPI). Your ISP probably already uses DPI to curtail the proliferation of computer viruses and unlawful downloads. VoIP data is infamously known to be difficult to scan. DPI can help find confidential data within VoIP data packets and also prioritize the transfer of VoIP data over your network to improve the reliability of the phone system.

Another tool to consider using is a Next-Generation Firewall (NGFW), a combination of a firewall and in-line DPI tool that helps prevent system intrusion. Businesses sometimes deploy a Unified Threat Management (UTM) system. This strategy unites a gateway anti-virus, firewall, and intrusion detection and prevention abilities in one digital security program. These systems can prevent security breaches by stopping sensitive data from leaving your network.

4. Vishing and ID spoofing

A few years ago, you probably heard of phishing, the practice of gathering private information via email, which could then be used in crimes such as identity fraud. Vishing is a combination of voice and phishing, and it is an attempt to collect private financial information over the phone. VoIP allows fraudsters to use new features of a VoIP system, like ID spoofing (displaying a name and number of their choice on the potential victim’s phone) to trick people in handing out confidential data.

ID spoofing may allow the caller to “show” the person receiving the call that they are speaking to a bank and, therefore, ease their sense of security. The best method to prevent this is to warn VoIP users to the possibility of such an attempt and to educate them on how to recognize and respond to a vishing inquiry.

5. Spam over Internet telephony (SPIT)

SPIT, also known as vam (VoIP spam), is when an unsolicited pre-recorded voice message is sent over a VoIP phone system en masse to thousands of victims. This is not a new strategy, as we have all been interrupted by telemarketers during our dinner at home. VoIP allows scammers to reach many more people much more easily. However, there are some simple solutions to this threat:

  • Consent-based communication
  • Reporting spammers and blacklisting them on internal systems
  • Audio Captcha (a recorded message will not be able to provide an answer to an audio captcha)

6. Protocols

A simple method to improve your VoIP system security is to turn off the services you aren’t using from VoIP service provider. The more protocols you have open, the more opportunities hackers have of attacking your system. Consult with your service provider to find all the services and protocols available, decide which ones you need and disable everything else.

IT departments are used to handling digital threats and are continuously implementing countermeasures. A VoIP system is not much different than working on your company’s internal network. There are threats, but the system is essential to get work accomplished in an efficient manner. Just like companies secure their digital networks, VoIP systems need to be protected as well. Your IT department should be aware of new strategies and software available to secure your VoIP data packets, and should continuously educate employees about serious threats and mitigating factors.


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