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THE STRAIGHT TALKING ALTERNATIVE

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How to protect yourself from toll fraud

What is the cost of global toll fraud

Source: (2013) Communications Fraud Control Association - Global Fraud Loss Report.

How Do People make Money from Toll Fraud?

Like all technological scams, people commit toll fraud because it is a brilliantly irritating combination of anonymity, profitability, and scalability. While there are as many different variations in approach as there are companies to exploit, primarily the scams that we see getting run use one of the following methods.

Phone Cards

International Numbers

In the first instance the person will sell phone cards with heavily discounted international call rates. When a consumer uses the card, their call is connected to the international destination via an unsuspecting company's PBX. Eventually the company will be hit with a massive bill for outgoing calls, rectify the security flaw, and the scammer will simply move on to the next unsuspecting victim. Because the scammer has passed off his primary cost structure, any money gained from the sale of the cards is money in the bank.

Premium Rate Numbers

High Cost Numbers

The second scam is conceptually much simpler because requires neither phone cards nor an unsuspecting third party. Once the scammer has control of a company’s PBX they places a series of calls to premium rate numbers that he/she owns (the kind people would ordinarily call to talk to a very special person for $12.99 a minute). But unlike your typical premium rate number, there is no special person at the other end, just a voice recording inanely muttering in order to maintain the verisimilitude of a conversation. This is done to minimise the chances that the call is flagged as fraudulent and dropped. Meanwhile the charges pile up, and the scammer pockets the proceeds.

How does Toll Fraud Work?

How do scammers get access to a PBX?

There are many different types of toll fraud and we won't be going into all of them today. Instead we are going to focus on the one we see as being the most pertinent to Australian businesses: PBX hacking. Typically a scammer will write a script that crawls the internet looking for vulnerabilities in companys’ firewalls (like open ports). Once an opening is detected, the scammer can then punch requests at it in order to tease out information about what the system is and how it might be vulnerable. Eventually they will have all the information they need to brute force their way through the firewall. For anonymity purposes and to reduce their own infrastructure costs, experienced scammers will do this via either a proxy, or a botnet (sometimes called a zombie network) of previously hacked computers.

Once the firewall has been breached the scammer can gain access to the PBX, build a back door into the system, and use it to route as much traffic through it as they think they can get away with.

What do Telco’s do to protect against it

From the Telco’s perspective (assuming it has been done elegantly) toll fraud is very difficult to detect. This is due to the fact that the traffic appears to be authentically originating from the company’s PBX with the source IP, user account, user ID, and password all matching the company’s records.

This means that some of the best tools in a telecommunications provider’s arsenal are the ability to monitor for the presence of toll fraud by scanning for atypical call activity, and the imposition of limitations to minimise the damage that can be done. For security reasons we will refrain from going into specifics, but the following list represents some typical strategies that providers employ:

Imposing channel limitations

Along with bandwidth limitations, toll fraud is one of the primary reasons that providers limit the number of concurrent calls that can be made from a single PBX. While this tactic may not actively discourage fraudsters, it limits the amount of damage that can be done over a short space of time. Because providers can see the number of calls that are attempting to connect (not just the ones that get put through) they are able to use this as an indicator of abnormal traffic activity. Additionally, because the vast majority of call fraud occurs to international numbers (see the picture below), providers will often impose separate limitations on how many concurrent international calls a customer can make.

Imposing a threshold on the maximum per minute cost of a phone call

Providers often impose an upper limit on the per-minute costs of calls that they are happy to connect, unless clients have specifically request that this limitation be removed. This limitation is used to prevent scammers from being able to dial premium rate numbers, such as 1900 numbers.

Limiting the amount of credit that a company is extended

In a worst case scenario, telecommunications providers seek to protect their customers from exorbitant call costs by placing an upper threshold on the amount of billable calls that a company is able to incur. The rules around this differ from provider to provider, and are likely to be dependent on the size of a company's average bill, so it is worth checking with your provider what your limit is and negotiating an increase or decrease as you see fit.

What can you do to protect against PBX Hacking?

Use complex and varied passwords

Time and time again we find toll fraud comes back to weak passwords. So even though it seems obvious, we are going to say it anyway: "Don’t use common passwords like 1234, password, guest, 1000, test, or the same four digit code as the extension phone". If you have trouble remembering your passwords, either use some secure software like Keepass to generate and keep track of them, or use a combinations that are easy to remember like “14CharlieSheen?” or "3BlindMice!".

Check your ISDN failover configuration

If you are using SIP based telephony, but have also chosen to maintain or setup a failover to an ISDN line, make sure your ISDN lines can’t be used to call high toll numbers. Why? Because if a scammer bombards your PBX with traffic, it is likely that some of the fraudulent calls, being unable to connect via SIP, will fail-over to the much more expensive ISDN connection.

Block country prefixes

Most PBX's allow customers to block outbound traffic to international numbers. So if you only conduct business domestically this is one of the best options available. Not only does it impose additional limitations on hackers, it is capable of preventing other less technologically advanced forms of toll fraud (such as late night staff making long calls to family members in other countries). Even if your business frequently needs to call international numbers, it is still unlikely that it will need to call all of them. As such, we recommended that you block all unnecessary destinations. Unless you have a clients or suppliers in these countries, this list of the top destinations for toll fraud call terminations might be a good place to start.

Where do most toll fraud calls terminate?

Source: (2013) Communications Fraud Control Association - Global Fraud Loss Report.

If your Telco also provides your WAN make sure you ask for a managed firewall

Telecommunications providers have a lot more experience with toll fraud than your average IT manager, and have become much more adept at configuring firewalls so as to minimise the chances of a breach as a result. If this option is available to you, we would suggest that you take advantage of it as it is going to make things a lot harder for the scammer.

Minimise the visibility of your PBX to the web.

If you are choosing to manage your own firewalls, wherever possible avoid leaving open ports available for staff to remotely access your PBX. Remember this is how most scammers are able to hack in, so avoid doing it unless it is absolutely necessary.

These are just a few of the techniques available and this list is far from all encompassing, but as with most technological scams, even implementing basic security measures makes a huge difference to how likely you are to be targeted. However, if you are interested in a more comprehensive solution, we would recommend talking to your telecommunications provider about what options they have available, and what they recommend for your organisation.

5 Major Advantages of SIP Over ISDN

For those who aren’t particularly familiar with the ins-and-outs of SIP and ISDN, the distinctions can be confusing and often outdated. To help clear things up we'll start with the basics and move on from there. SIP or Session Initiation Protocol is an application layer protocol that is based on IP. Without getting into the gritty details too much, it’s more or less the communication standard responsible for VoIP (Voice over IP) telephony. Whereas ISDN (Integrated Services for Digital Network) is a much older communication standard designed for the transmission of voice traffic over traditional phone networks.

In practical terms, both services are delivered in a similar way, and can achieve similar levels of reliability. However, in an ISDN deployment (Diagram 1), businesses are required to pay for and run both a voice service (indicated by the dark grey line) in addition to their data services (indicated by the light grey line). Whereas in a SIP deployment (Diagram 2) a singular system can be used for both voice and data services, saving a significant amount of costs to the business.

Diagram 1 - ISDN Based Call Routing

ISDN Based Voice Routing

Diagram 2 - SIP Based Call Routing

SIP Based Voice Routing

There are a myriad of advantages that SIP can offer businesses over ISDN, and we’ve outlined a few of the major ones below.

1. Scalability

ISDN services are typically limited to the channel blocks in which they are bought (typically 2, 10, 20, or 30), whereas SIP is deployed across a business’s existing WAN. Meaning that provided the bandwidth exists to handle the traffic, channels can be dynamically added or subtracted as they are required. This has the advantage of limiting the amount of unused overhead that has to be purchased in an ISDN model, as well as allowing the business to be able to ramp up the number of SIP channels within minutes, as opposed to the days or weeks required for ISDN.

2. Portability

In a typical Australian ISDN deployment the line and channel block comes with an allocated phone number. The rental charges for which are automatically factored into the cost of the ISDN, whether or not it is needed.

In a SIP based service numbers are separate from the channel blocks, which has the benefit of helping to lower the cost of the service. However, the main benefit is derived from the fact that the phone numbers are not tied to physical locations.  This means that calls to SIP numbers can be diverted incredibly easily to other locations. Typically this is done as an automatic failover between multiple office sites, allowing calls for one site to be answered by another site when all the lines are busy.

This same functionality also allows numbers to be redirected in disaster recovery situations. For instance, if a business’s premises were to flood, the phone lines could easily be redirected to a single (or multiple) recovery sites until such time as the service could be restored.

3. Interoperability

SIP voice is transferred as IP (Internet Protocol), this means that customers with video enabled handsets can make video calls. Although, this kind of functionality is available on an ISDN service - some of the more tenured readers may remember the Telstra Megalinks of the late 90's and early 2000's - the bandwidth requirements of video over ISDN make this an economically unjustifiable option in today's marketplace.

4. Quality

Because SIP can be delivered across high bandwidth connections (such as Fibre, EFM and EoC) higher levels of vocal quality can be delivered from end to end. This means that customers can make and receive HD quality voice calls, assuming of course their hand sets are compatible. Additionally, with services not necessarily relying on a single connection, SIP services could utilise a primary service with automatic failover to a second path, which is not available on ISDN.

5. Price

The bottom line is what it often comes down to for businesses, and for the reasons outlined above SIP almost always wins out over ISDN.

One of the biggest benefits of a SIP based solution over an ISDN solution is illustrated by the dashed lines in Diagrams 1 and 2 above. In an ISDN solution an internal call (ie. a call from one site office to another) is required to traverse the PSTN (Public Switched Telephone Network) in order to reach its destination. This comes at a cost to the business because it is handled the same as any other call. Additionally, it also requires the purchase of a PRI (Primary Rate ISDN) for each of the sites.

In a SIP deployment the call remains within the business's MPLS network and is therefore able to avoid the charges for call handoffs by their telecommunications provider. Although external calls will still need to be handed off to the PSTN, because SIP traffic is IP based it is capable of traversing the company’s own MPLS WAN and being handed off without the need to purchase PRI's.

Even for small businesses this can add up to a lot of savings. Exact figures will obviously vary from business to business, but if you are still using an ISDN based service we would recommend having a chat to your service provider to see what opportunities are available.


If you are interested in finding out about Over the Wire’s SIP based voice platform learn more on our IP Voice Product Page, or contact our team to have a discussion.

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