Keeping telephony secure

Keeping telephony secure

The threat of fraud has always been one of the greatest concerns for businesses up and down the country.

Much has been made of the security threats posed to a company’s IT infrastructure, especially given the rise of ‘bring-your-own-device’ trends and mobile or flexible working.

However, there is more evidence to suggest that many hackers are increasingly looking at more traditional ways in which to hack into a company’s system.

The phenomenon of toll fraud is one that many businesses may have heard of before, yet there is an overwhelming level of naivety among many decision makers, many of whom seem to think that it is a problem that largely does not exist in the UK.

A number of criminals are taking advantage of this lax approach, using toll fraud schemes to dial into a company’s phone system in order to route calls to other destinations, usually abroad at the expense of the organisation.

Even in cases where companies are aware of the dangers, such malicious activity is usually difficult to detect as it doesn’t become obvious to companies until they receive their phone bill at the end of the month.

When one considers the fact that, in the current business environment, not taking a serious attitude to security can prove to be hugely costly and this extends to traditional telephony, as well as converged voice and data networks.

Financial Fraud Action UK recently claimed that telephony scams are defrauding a number of small businesses out of hundreds of thousands of pounds.

Telecommunications is the fourth largest expense on a company’s profit and loss sheet, meaning firms need to ensure they have measures in place that ensure they do not get caught out.

How it works

Toll fraud uses two common methods. The first is using the voice mail ports of a telephone system. Systems are often more vulnerable if the customers’ main incoming number is handled by an Auto Attendant (AKA IVR system).

If these voice mail ports are left open (for dialling external numbers) it can often create a window of opportunity for hackers.

The other method being exploited by fraudsters is call forwarding and Diversion or Direct Inward System Access (DISA) Number.

DISA is used by telephone system administrators to allow home workers to dial in and make external long distance calls, clear or setup call diverts, clear message warning lights and enable users to ring the DISA number followed by the internal extension (if the users do not have DDI).

However, the main danger of DISA is that it could leave a company’s system vulnerable to attacks, many of which see criminals trying to obtain unauthorised access to the same resources.

SIP toll fraud

SIP is replacing ISDN as is now the preferred PSTN connection for the majority of businesses. As this is new emerging technology there are still security loop holes, for example:

  • Leaving the user name and passwords for the Installed SIP device to ‘1111’ or ‘2222’ (If SIP phones are used as external stations)
  • Without solid protection the PBX will assume an incoming call is coming from a SIP phone, automatically log it and provide dial tone. This allows the hacker to dial out by inserting ‘9’.
  • Arrow recommends the use of SIP Border Gateways (SBG/ MBG) that support alphanumeric passwords and to lock firewall ports.


A number of high-profile firms have already decided to take action and close any potential loopholes in their security.

However, some areas of vulnerability may be a little more complicated, especially if you happen to be a small or medium-sized business that lacks the expertise to find the problems.

Fortunately Arrow has the ability to carry out a full review of your infrastructure and advise where enhancements to the security of your telecoms estate can be made to safeguard your organisation moving forward.  Working alongside our suppliers we can recommend how restrictions can be made to your existing system and in some cases investigate the benefits of adding specific Fraud detection and Prevention Modules.

Find out more by calling us on 0333 240 9880 or email us