Calling Line Identity (CLI) seems innocuous, but when you look at it, it is central to so many areas of telecoms that we all need to be on top of this topic.
At the most basic level, CLI informs a person of who is calling them. Still, we also use it to identify where calls originate within the network, and many billing systems rely on it for correct call charging. Some systems even use it to make intelligent call routing decisions.
When everything works and CLI is used legitimately, this is widely accepted as a reliable industry standard. However, the challenge comes when there are technical issues or nefarious users.
Since many networks have migrated to IP, we have found a variety of use cases that don’t comply with UK standards, most of which are getting ironed out by cooperation between carriers and service providers, thankfully, but for a while, it wasn’t unusual to discover that a CLI flagged for withholding by the caller was in fact passed on to the called party, or that a ‘network’ CLI has been used for presentation instead of the separate number provided for that purpose. In fact, the number of interoperability issues we uncovered led to the creation of our Mag-Hub solution, an interconnected platform that manages the variations between carrier networks meaning far fewer issues are experienced by the called or calling parties.
Whilst these technical challenges are starting to be far less frequent, thanks to networks undertaking better testing and greater awareness of standards, the arguably much larger concern is that of scam and nuisance calls. With a spotlight on this from the highest ranks here in the UK, Ofcom find themselves under pressure to stamp out this age-old misuse of our telephony network.
We all appreciate the ease of use and flexibility that comes with a modern IP telephony network. However, with that flexibility comes simplicity for the less honest in our society to manipulate CLI data to improve their chances of having calls connect or to convince people of their identity.
Common scams include callers pretending to be from banks, insurance companies and the like, and by presenting a legitimate-looking CLI, the caller is frequently duped into believing everything is genuine. The end result is they give out more information than they safely should, with sometimes dire consequences for the individual concerned.
Nuisance calls, on the other hand, often arrive with genuine-looking CLI to improve the chance of them being answered. Still, then when the called party tries to return the call or raise a complaint, we discover the CLI was, in fact, ‘spoofed’ and is either invalid or belongs to an entirely different organisation. In these scenarios, the only way currently to trace the source of the call is to work backwards through the call path to discover the call originator. This step is rarely taken as it can be costly and time-consuming even if you do get all parties to co-operate.
Part of the challenge here in the UK is that we don’t have a simple way of validating the legitimacy of a CLI after the call leaves the originating network. Obviously, we can all do basic checks such as making sure it ‘looks and feels’ like a real number and of course, we can ensure all suppliers and client contracts include an obligation to use only CLI in accordance with the regulations. But this doesn’t appear to be enough to significantly reduce the number of scam and nuisance calls. According to Ofcom, the problem is as serious as ever, and this has caused them to consult again on further steps we can take as an industry.
