Category Archives: Security

Scammers making use of Telstra landline bug – part 4

It is a good idea to keep your computer systems up-to-date, by installing the latest software fixes. But there is one fix that Telstra needs to request and install, to fix a bug lurking on Telstra’s landline telephone system which scammers are making use of.

This is Part 4 of 4 of Scammers making use of Telstra landline bug.

  • To learn about the scam, read Part 1
  • to learn more about testing your landline and protecting yourself, read Part 2
  • To find out how I became an unwitting victim 21 years ago, read Part 3.

Here, we explore some myths and facts about this bug, and I have some requests for information (please comment if you can answer any of the questions).

Facts and myths

Scammers can intercept calls you make (shortly after they call you)
They’re intercepting all calls that everyone is making to 000, or the bank
The truth: there’s been a few crimes like this in the past (against radio stations), but not this time. Only one person’s calls get intercepted.
An evil caller can control your landline, preventing you from making calls, for up to five minutes.
Scammers can make calls to sex lines in Nigeria from your line
The truth: They cannot; if you see such calls on your bill, it was probably a family member or employee.
Scammers can imitate the bank’s phone menu (or they could make a temporary, actual connection which they cut off at the right time)
This bug enables them to fake my Caller ID
The truth: A separate hack applies to Caller ID, which the scammer might also use as part of their fraud.
An evil caller can prevent other callers from getting through to you (they get busy tone).
They can listen in on everyone who calls you
The truth: They have to physically wire a listening device across your line to do that. The method described here only allows a scammer to intercept calls you make, shortly after their call.
There is no indication if a call is still connected on the line after you hang up.
A scammer can be secretly connected to your line at any time
The truth: It doesn’t “just happen”. They have to call you first, and the effect only lasts for five minutes (maximum, in Australia).
Mechanical exchanges also had this characteristic

Map of Australia showing various towns.

Land of the Long Held Call[1]

Map of New Zealand showing various towns

Land of the Long White Cloud[2]

Every country operates like this
The truth: Only a few countries have this bug. New Zealand, Canada, the U.S., and many other countries do not have this bug. And mobile phone systems do not have this bug, either.
Various scams and tricks arising from this bug have been in use for some time. In the past, there was no five-minute timer, so it was possible to lock out someone’s line for weeks. Journalists and reporters, having interviewed someone for a story, would leave the call open preventing competeting journalists from calling their victim and getting the same story.
Surely the Police would speak to Telstra about this?
The (horrible) truth: I’m not convinced it’s even occurred to them that it’s a bug, nor am I convinced that they’ve actually spoken to Telstra about it. But I am sending information to the Police about this, firstly to ascertain what has transpired, and secondly, (from a crime prevention perspective) to persuade them to be more on the front foot with Telstra on this issue.
The only sign of action by the authorities I can find is the British Financial Ombudsman Service has called for action by (British) telecoms companies to remedy the flaw in hanging up phone lines.

Where is the bug?

It is in the telephone exchanges – specifically, the software running inside the exchange. This has to be fixed, either by the manufacturer of the telephone exchanges (Ericsson), or by someone changing a configuration setting. Telstra has to request this in either case, and it is likely to take 3-6 months to fix.

The official term for this is CSH (Called Subscriber Held) or A-party Release. I call it a nasty bug, but unfortunately, it is hard to convince Telstra that this needs fixing.

I have some questions

While researching anything like this, it is natural for questions to arise. Does anyone have information on anything below, or anything else? Please leave a comment.

Note that comments usually require approval before appearing, which I generally check three times a day … agree or disagree, I approve “anything” on-topic.

  • Australia: Does anybody using Optus Cable (or other HFC services) experience the problem? Please do the test to find out.
  • New Zealand: Did CSH apply on Crossbar or Step-by-Step exchanges (say, before 1980)?
  • New Zealand – TelstraClear subscribers: Can someone do a test, to see if CSH applies to Telstra’s exchanges in NZ?
    You are probably a TelstraClear subscriber if your telephone number begins with 9xx xxxx, and if your TelstraClear bill shows a line item for Telephone Line Rental or Monthly Charges.
  • Britain: There was a proposal to reduce the CSH hold period to 10 seconds. Was this implemented?
  • U.S.: I don’t want to believe the movies too much 🙂 but they frequently show the B-party hanging up and the A-party receiving dial tone. Is that true?
  • All countries: Please do the test. It’s for your benefit to be aware of the situation, as well as our curiosity 🙂

If you have information, please fill out a comment (note: DELAY before it appears, for most people).


Scammers making use of Telstra landline bug – part 3

Oops, a change of plan

It is only just this week that it occurred to me that I was most likely an unwitting victim of this bug, 21 years ago (early 1995). The planned Facts and myths about this landline bug will now be Part 4.

This is Part 3 of Scammers making use of Telstra landline bug. Read about the scam in Part 1, and learn how to test your landline for the bug in Part 2.

An unwitting victim

I was not able to call for an ambulance to a neighbour’s kitchen knife accident.

Of the six people involved in the incident, only my wife and I understand English clearly, which added to the problems/confusion.

My mother-in-law was visiting neighbours when she called out to us there had been an accident in the kitchen (and then continued in Khmer[1], to my wife). I rushed into the house and saw the mother and son huddled together. The mother was clearly distressed, and there was quite a bit of blood, but there was no ongoing blood loss and they weren’t losing consciousness, so I picked up the phone to call 000. But there was an Asian voice on the line.

Queensland Ambulance Service vehicle


I hung up for a few seconds, but the voice was still there, saying “Hello, hello”. Despite saying “please hang up”, and “Emergency here, please hang up”, it was a case of message received but not understood. I asked the victims where the other telephone was (thinking the voice was on another telphone extension somewhere else in the house, unaware of the drama). And I raced around the house and into the bedroom, but found no-one and no other telephone. We had just moved in and didn’t have our own telephone, so after trying the telephone once more, I ran to the payphone down the street and called the Ambulance.

The Ambulance eventually came and took them to hospital.

In the days and weeks afterward

Me, my wife, and my mother-in-law had come from New Zealand a few months before, where one can disconnect a remote caller by simply hanging up, provided that no-one else on your line has another phone off-hook.

Diagram showing a telephone call from phone A to phone line B which has two phones, B-x and B-y. Phone B-y is off-hook talking to A. Phone B-x is on-hook (idle)
Diagram of telephone call[3]
In New Zealand, phone B-x can get dial-tone provided phone B-y also hangs up.
In Australia, phone A must also hang up.

Referring to the diagram above, I raced around the house looking for phone B-y. But my mother-in-law knew the neighbours quite well and clarified there’s only one phone in the house, and that it was working (the day after), leading me to assume that it was on a party line[4]. They were unusual in urban areas, but one of my own friends had a 2-party line in Johnsonville (NZ) in 1989 – so it definitely wasn’t impossible.

I will never be absolutely certain of the truth, but it wasn’t until a few weeks after the scam story broke, and a few days after I wrote Part 2 that I realised that this bug is a much more plausible explanation for the difficulties. It means that in Australia, both the A-party and other telephones on the B-party’s line must hang up before the B-party can get dial-tone.

This has to change.

UPDATE Part 4 – Facts and myths about this landline bug is now available.

Links and Footnotes

Scammers making use of Telstra landline bug – part 2

TL;DR(1) – Telstra has a bug in their landline system. It’s time to get rid of it for good.

TL;DR(2) – The bug is when someone calls your landline they can prevent you from hanging up. Find out how to test, and how to protect yourself from scams.

This is Part 2 of Scammers making use of Telstra landline bug. Read about the scam in Part 1.

Yes, it is a bug

Bug, n:
An error in software[1] that causes results to be different from expected.

Mug shot of mean-looking man

Section 7.2.1? Just gimme a phone that works[2]

Let’s get one thing straight: I’m calling it a bug … #CallASpadeASpade. I certainly understand the people who point out the phone network complies with Section 7.2.1 of BT SIN 721 [pdf] (or Australia’s equivalent), but that is extraordinarily unhelpful. Most people expect calls to disconnect when they hang up. Therefore (to most people) it is a bug.

Now that’s out of the way, on to checking your landline for the bug, and protecting yourself from scams.

Testing your landline (easy)

Instructions for testing:

  1. The most reliable test is from another landline,[3] within the same local calling area. So you should ask a friend or neighbour. The caller is the A-party, calling your landline (the B-party).
  2. The A-party calls the B-party who answers.
    RESULT: A & B parties talking.
  3. B-party hangs up.
    RESULT: A-party hears silence.
  4. [OPTIONAL] Using a mobile phone or similar, quickly call the B-party.
    RESULT: False busy tone.[4]
  5. B-party picks up (within 30 seconds).
    RESULT: They connect back to the A-party. A & B parties talking.
  6. B-party hangs up. The A-party should time how long it takes before they hear disconnect (beeping) tone.
    LIKELY RESULT: 30 or 90 seconds, but could be five minutes.
  7. Repeat the test, but A & B parties should swap roles.
    Here, you’re doing your friend a favour by testing their landline for the same bug.


The official term is CSH (Called Subscriber Held) or A-Party Hold Release[correction]. I call it a very nasty bug because the victim (having received an unusual call) believes they’re doing the right thing by initiating their own call to verify the circumstances, but in reality they are still connected to the A-party scammer. This bug can be used in many different ways by different scammers, particularly to glean private information from the victim, but it is also possible to simply cause confusion, or lure someone to their death.

Continue reading to learn if a scammer is still on your line after a call.

How to protect yourself

Every man and his dog is making calls[5] (video, 0m59s)

By now, every man and his dog will have called each other and concluded their landline is vulnerable. Based on discussions with Internode (my telephone provider), Telstra has informed them that there is “nothing that can be done”. Even if they change their mind, it might take three to six months.

So, in the meantime, if you get any strange call (or they hang up just as you answer) stop and think. If you call someone else quickly, you might fall victim. You have to check your landline is genuinely free.

Probably the best way is to use your mobile telephone to call your landline; you should hear ringing through your mobile, and hear the landline ringing[4]. You don’t have to answer your landline, so hang up (end call) on the mobile, to avoid being charged. If you can’t do that, there have been some other suggestions from various people.

  1. If you have a toll bar on your landline, call a barred number. The wording of the message should be exactly the same.
    Perhaps you should organise 1900 barring now, if you don’t have it already.
  2. Call a trusted friend or loved one. BEWARE: The scammer may still be on the line, eavesdropping.
  3. Sidestep the issue by using a different telephone (or mobile telephone) to make your outgoing call (to the bank/police).
  4. Wait five minutes for the line to clear
    The problem with this is clearing times vary significantly, and the scammer could simply defeat you by calling you again at the four-minute mark.

Complexity, complexity, complexity

Australians have a habit of making simple things complex (yes, train tickets in Melbourne are too complex for tourists and locals), but I am still stunned that the act of hanging up the telephone is this complex.

I am entitled to think that it will work as expected (as it does in New Zealand).

And I’m entitled to think that a scammer will not be able to interfere with the use of my telephone, or any other technology. CSH (as it is termed) should have died with the last mechanical exchange, and it is time to get rid of it for good, in order to protect people from fraud[6], as well as make the phone network simple to use.

UPDATE (and change of plan) Part 3 is now available as How I was an Unwitting Victim – 21 Years Ago.
The planned Facts and myths about this landline bug will now be Part 4.

Links, Footnotes, and Updates

Scammers making use of Telstra landline bug – Part 1

TL;DR – When someone calls your landline, they can prevent you from hanging up, and intercept calls you make afterwards.

There is a bug lurking on Telstra’s landline telephone system which scammers are making use of. The scam is described in The Age; it usually runs like this, where a scammer (the A-party) calls a victim (the B-party):

IMPORTANT NOTE: If you are receiving malicious calls, speak with your telephone provider (most have procedures to trace calls). If these calls are life threatening, call the Police on 000, within Australia.

On the phone to the "bank"

Telephone fraud

This is the Rolex Store manager here. Someone has attempted to use your credit card here. Please call your bank straight away and cancel your card.
Thanks. (hangs up) [NOT TRUE: Call is still connected because A-party has not hung up]
(picks up receiver, hears dial tone) [NOT TRUE: Scammer is playing fake dial tone]
(Dials the number, hears the usual bank menus, and gets through to someone [Actually: the scammer’s mate].
The scammer’s mate tells a false story of an attempt to withdraw the entire victim’s savings account and pretends to place "Red Alerts" on the account.

Some days and several calls later, the victim is told the only way to protect the money is to transfer it to a "Safety Deposit" account with Barclays in the UK until Police investigations are concluded. Several victims have complied, losing $5m in the process.

While the Fairfax media (The Age) goes into the fraud in some detail, they only make cursory mention of a "long-held" cold-call scam, and they don’t even identify it as a bug.

A Software bug

The bug is that when the B-party hangs up, the call does not disconnect. It only disconnects if the A-party hangs up, or if a timeout expires[1].

It is a very nasty bug, because most people believe that if they initiate their own call to the bank (or Police), the call is safe. The bug does not occur in New Zealand; the call disconnects as soon as either party hangs up. This has always been the case (30+ years)[2] [3].

Like any security bug in Linux/Firefox/Windows/Oracle/etc, the question naturally arises: when can we expect a fix, and what are the precautions/workarounds?

It is Telstra’s responsibility to fix this bug.

UPDATE Part 2 – how to test your landline for the bug, and ways to protect yourself is now available

Links and Footnotes

Chrome starts blocking web sites using HTTPS over SSL3

It would seem some organisations still haven’t got the message on SSL vulnerabilities, even one with a publicity-friendly name like Poodle.

For instance, Swinburne University of Technology, which is actually one of Australia’s better universities to learn computer science, has its student portal still trying to use SSL 3.

MySwinburne SSL error

My son was trying to figure out why he couldn’t connect with Chrome. Only by clicking for details do you get the slightly cryptic error: “ERR_SSL_FALLBACK_BEYOND_MINIMUM_VERSION”

It turns out Chrome has disabled fallback to SSL3. For now you can override it (though it’s easier for now just to use another browser), but soon it’ll be disabled completely. Site owners will need to make sure their servers support TLS instead.

They’ve also started giving a warning on SHA-1 certificates — no more green logo; it’s gone yellow, with a warning: “This site is using outdated security settings that may prevent future versions of Chrome from being able to safely access it.” Again, it’s up to site owners to resolve this, by updating their certificates. malware

Interesting warning from Google when displaying some pages on this

Malware warning

In response I’ve disabled the Socialize plug-in which was serving them. Hopefully that makes the warning go away — I’ll look for another way to display social media buttons.

Airliner shootdowns ought to be technically impossible

Using missile to shoot down an airliner ought to be made impossible.  It may be a lack of imagination on my part, but I can’t think of a circumstance where a military force needs the ability to shoot down civilian aircraft.  There aren’t a lot of manufacturers of surface-to-air missile systems, regardless of their level of sophistication and range – shoulder launched or vehicle-mounted – so changing those designs to prevent civilian shootdowns ought not be a big deal. Admittedly there are many more means of bringing down aircraft beyond SAMs, but not a lot of them have the reach to bring down cruising airliners.

Civilian airliners have carried IFF transponders since World War II, so there’s the infrastructure in place already for the identification of non-military aircraft.  Furthermore, it’s a violation of Article 37 1.c of the Geneva Conventions to pretend you’re a civilian – that is, it’s a war crime with all the international condemnation that goes with that, so it’s reasonable to make weapons that refuse to down aircraft that identify themselves as civilian.

So, why is this still happening?

Tap and Go causes crime: duh

Ken Lay says that in the last year in Victoria, 11500 extra crimes caused by Tap and Go cards have meant that the crime rate in Victoria has gone up (5%) rather than down.  These additional “crimes of deception” and are apparently tying up police.

It’s slack. Totally slack. There’s no control over it. And what are we finding? There’s been a huge spike in different offences committed to facilitate it; cars being broken into, mail stolen, handbags grabbed, purely because of industry introducing a new practice without any regard to security.

We have taken the view we should be taking on industry over this because our concern is they’ve introduced new practices with no regard to the implications on security and there’s no prevention measures, which is at times bogging down our members in work and time that could be better spent on some really serious type of investigations or responding to critical issues.

Assistant Commissioner Stephen Fontana

And the ABA says “no ways!” and says that dollar value of fraud is down since chip-in-card (neglecting that this isn’t about that) but allowing that losses following theft are up 35% (to only $20m/year).  And ignores all the crime that would be associated with obtaining the cards.

Programmatically create Django security groups

Django authentication has security roles and CRUD permissions baked in from the get-go, but there’s a glaring omission: those roles, or Groups, are expected to be loaded by some competent administrator post-installation.  Groups are an excellent method of assigning access control to broad roles, but they don’t seem to be a first-class concept in Django.

It seems that you can kind-of save these values in by doing an export and creating a fixture, which will automatically re-load at install time, but that’s not terribly explicit – not compared to code. And I’m not even sure if it will work.  So here’s my solution to programmatically creating Django Groups., which is created in the same directory as your and is automatically run during python syncdb:

from django.db.models import signals
from django.contrib.auth.models import Group, Permission
import models 

myappname_group_permissions = {
  "Cinema Manager": [
    "delete_ticket",         # for sales reversals
    "add_creditcard_charge", # for sales reversals
  "Ticket Seller": [
  "Cleaner": [ # cleaners need to record their work

def create_user_groups(app, created_models, verbosity, **kwargs):
  if verbosity>0:
    print "Initialising data post_syncdb"
  for group in volunteer_group_permissions:
    role, created = Group.objects.get_or_create(name=group)
    if verbosity>1 and created:
      print 'Creating group', group
    for perm in myappname_group_permissions[group]: 
      if verbosity>1:
        print 'Permitting', group, 'to', perm

  sender=models, # only run once the models are created
  dispatch_uid='myappname.models.create_user_groups' # This only needs to universally unique; you could also mash the keyboard

And that’s it. Naturally, if the appropriate action_model permissions don’t exist there’s going to be trouble.  The code says: After syncdb is run on the models, call create_user_groups.