Brian Moreau

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Mobile phone hacking and tapping.

The allegations
In the news as of 9th July 2009 is an allegation that the News of the World hired private investigators to hack or tap into thousands of mobile phones belonging to politicians and celebrities.

Is that hacking or tapping?
What I find frustrating about this story is the apparent lack of understanding of the difference between hacking and tapping by both the media the police and politicians.

One story reports on phone hacking and yet a reply from the police state there is insufficient evidence that any tapping has taken place.


Hacking and tapping are two very different activities although if there is any truth in this I would assume that given the money involved in stories of high profile people then it is vey likely that both voicemail hacking and phone tapping are both taking place.
I would also assume that various other forms of bugging are also being used.

Because their are so many conflictions in this story I am going to explain the difference between tapping and hacking for the benefit of the media, the police and anybody else who may find this of use. I will also show how easy it is to conduct such activities and why no evidence can be found to prove if any voice mail hacking or phone tapping has taken place.
A fact the police should be able to recognise.

Mobile phone voicemail hacking
Although there are many forms and methods of mobile phone hacking this story appears to relate to the unauthorised access of voice mail.
Many of us simply don’t use voicemail on a mobile phone never mind realise that voice mail messages can be accessed remotely i.e. from a phone other than the mobile phone that the message was left on.
I will explain how easy it is for you and any anybody else to listen to your messages.

On receiving a voicemail the mobile phone operator will send a text message informing us that a voice mail message has been received, the message usually contains the telephone number of the voice mail retrieval system and will give you the option to automatically dial that number.
The phone system recognises the number you are calling from and automatically connects you to your voicemail.

The first and most obvious method then if you wanted to access someone’s voicemail is to “borrow” the mobile phone, unless you was a close friend it would be hard to do this however if you left your mobile unattended maybe while you sleep or have a makeover it leaves it venerable to being used without your knowledge.
Even someone you trust may deceive you if they are offered enough money. Friends usually have a price too.

Ok lets assume you can’t get hold of the phone in question is their another way?

Mobile phone cloning
As explained above the mobile phone network recognises your mobile phone number on the network, this number can in fact be programmed into another mobile phone, this is called mobile phone cloning and was rife a few years back and allowed you to make free calls which would be added to the victims bill. It is however much harder to achieve these days but not impossible if you have the necessary equipment.

No mention of mobile phone cloning has been reported but I just thought I would mention it as an option that may have taken place.

Remote voicemail access
I will now deal with remote voicemail access.

The pin code
To access your or someone else’s voicemail remotely or from another phone all you have to do is phone the voicemail number which varies between mobile phone networks, enter the phone number of the phones mailbox you wish to access and enter a 4 digit pin code.

It is this pin code that makes the system very insecure as in most cases if you have not actually set a pin yourself then a default code of something like 0000 or 1234 is preset.
Even if you have set up a personal and private pin code because humans are very forgetful and creatures of habit we will invariably use our date of birth or a number that has some significance to us that we can easily remember. These are probably numbers we use for the lottery too so getting hold of someone's old lottery ticket, or knowing their date of birth could reveal someone's pin code. Note that pin code is very likely to be someone’s cash card pin too as we often use the same code for all of our devices.
You don’t have to be a private detective to work out what the implications of that are.

Guessing or hacking the pin code
If the above methods do not work you could always try to guess the pin, after all there are only 4 digits however there are 10,000 different combinations so it may take you some time however their is a way to crack this code in a matter of hours if the phone network will allow it.

DTMF Tones
When we dial a telephone number you hear different audio tones in the earpiece of the phone, each number has its own unique tone at a specific frequency, when we enter our voicemail pin code these tones are used for this too.

You may not realise it but these tones can actually be played down the handset and the exchange won’t know if you are pressing buttons on your phone or playing tones, as long as the tone is of the correct frequency then it will understand what tone related to which number and dial that number.

Tone diallers
There are actual devices called tone diallers, these diallers usually pocket size reproduced the necessary DTMF tones to dial telephone numbers. Some were even built into watches. They were ideal for business people using pay phones because they could store all you business contacts and friend’s numbers, they also speeded up dialling.

Most phones especially mobiles have a built in directory now so these old tone diallers are more or less obsolete however I am sure you can still buy them and it would not be to difficult for someone competent in electronics to build one, you may even find one at a car boot sale.

Custom DTMF tone dialler
A computer could also be programmed to output these codes via the speakers and a quick search on Google reveals several code generators that you can download and install on your computer.
So how can a tone dialler hack voicemail? Simple as it is electronic it can be programmed to repeatedly dial all the combinations until it got the code correct which could theoretically be accomplished in a few hours.

Can it be traced?
Well yes but at present no, I contacted all the common UK mobile phone networks and none said they log the number that voicemail is accessed from only the time the message was accessed is logged.
The only evidence you have that your voicemail had been listened to by someone other than yourself is the fact that the messages status becomes marked as “old” as opposed to “new” however you can’t prove to the police that it was not you that listened to it.
If the message is deleted by the unauthorised listener then you will not even be aware that you had a message in the first place. How many times have you sent an SMS or voicemail that the receiver has never received? Any complaints could easily be dismissed as technical glitches.

Can it be stopped?
Yes the mobile phone service providers could easily log all the numbers that access the voicemail system in exactly the same way I log all the visitors to my web sites.
Secondly the number of incorrect tries to enter a voicemail pin could be recorded and the operator could lock out after say 3 incorrect tries and notify the owner again in exactly the same way your cash card will be withdrawn if you repeatedly enter an incorrect pin.

I guess that nobody ahs really considered that these messages are of any security concern.

Note home answering machines also suffer from this pin tone vulnerability and I wonder if the private investigators were also intercepting these.

Because this article ended up far longer than intended I will deal with tapping in another post however tapping usually refers to listening to or bugging of a phone conversation which is obviously very different.

Another point to note is the voicemail hacker will need to know what network the number is on. This can be achieved in a number of ways such as using a telephone number look up tool on the internet or calling the phone when it is switched off.
In the later case the operators name is usually announced when leaving a message.
“Welcome to the O2 voicemail messaging service for number”
Operators could omit that information thus making it harder to find out what mobile network someone is on.

UPDATE October 2010

I have received quite a number of requests for voice mail access numbers and default pin codes. I have yet to complete the full list and would thus appreciate it if anyone could send me the missing data.

Voicemail Access
Default PIN
Enter mob num + #
Enter PIN + #
T Mobile
Mobile Number
Mobile Number
* PIN Max 3 tries
Mobile Number

* Unverified Data

Systems that require access by calling the mobile number itself are probably the hardest to hack since the phone will need to be switched off or out of signal otherwise the phone will simply ring.
Next time your phone rings and the caller instantly hangs up before you have had time to answer it could be someone attempting to hack your voicemail.

Click here for the article regarding Telephone Tapping

HTC range

UPDATE February 2014
Since writing this article back in 2009* we are still seeing people investigated for voicemail hacking.
I’m glad they finally managed to learn the difference between hacking and taping and I also see that most mobile phone operators have now made it much harder to access someone else’s voicemail remotely by eliminating the default PIN.
This prevents your voicemail being accessed remotely until you have set a PIN.
Thus now unless you know someone’s PIN or have a good guess it is very unlikely you will have other people listening to your messages.
I wonder if the mobile operators lock your access after a certain amount of incorrect tries and log the telephone numbers that attempt access.
This may at some point be an inconvenience to the genuine user if they forget their PIN but also make voicemail hacking just about impossible and traceable if unauthorised access is granted.


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Mobile phone hacking and tapping
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