11 Mar
2016
11 Mar
'16
2:05 p.m.
Hi,
I would like to know what are the capabilities of the silent-call implemented in OpenBSC.
When I try the command from VTY, I do not get any useful information from the target.
Should it be like a normal call where I can listen to the called number but without having
the target notified?
Best regards,
Robert,
11 Mar
11 Mar
2:15 p.m.
Hi.
No, the silent call has nothing to do with audio - getting access to
target's mic without it noticing is not part of GSM spec so in order to
implement it you've got to exploit some bug in phone's baseband. I think
it's being done couple of times successfully.
Silent call in OpenBSC is about initiating "pre-call" signaling so phone
"wakes up", allocates the channel to BTS and waits for further
instructions. Normally, the instructions to start ringing, display
caller number etc would follow but not in this case. This is perfectly
within GSM spec. The point is to get low-level connection to the phone
so, for example, it's current position could be requested over RRLP. Or
to test smth.
Out of curiosity - what kind of information would you find useful in
this case?
On 03/11/2016 03:05 PM, robert wrote:
Hi,
I would like to know what are the capabilities of the silent-call implemented in OpenBSC.
When I try the command from VTY, I do not get any useful information from the target.
Should it be like a normal call where I can listen to the called number but without having
the target notified?
Best regards,
Robert,
--
Max Suraev <msuraev(a)sysmocom.de> http://www.sysmocom.de/
=======================================================================
* sysmocom - systems for mobile communications GmbH
* Alt-Moabit 93
* 10559 Berlin, Germany
* Sitz / Registered office: Berlin, HRB 134158 B
* Geschaeftsfuehrer / Managing Directors: Holger Freyther, Harald Welte
3:04 p.m.
Hi Robert,
On Fri, Mar 11, 2016 at 04:05:15PM +0200, robert wrote:
I would like to know what are the capabilities of the
silent-call
implemented in OpenBSC. When I try the command from VTY, I do not get
any useful information from the target. Should it be like a normal
call where I can listen to the called number but without having the
target notified?
a silent call is a pure signalling connection, it does not have any
actual voice data. It serves primarily the purpose of turning the MS
into a permanently (on one TS) transmitting beacon that can be localized
using various radio-localization techniques.
We implemented the feature in order to demonstrate/show-case some of the
GSM "mis-features" that are being abused by signalling intelligence /
law enforcement devices.
--
- Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/
============================================================================
"Privacy in residential applications is a desirable marketing option."
(ETSI EN 300 175-7 Ch. A6)
3:35 p.m.
Hi,
Thank you for this explanation.
Best regards,
Robert,
On Mar 11, 2016, at 5:04 PM, Harald Welte <laforge(a)gnumonks.org> wrote:
Hi Robert,
On Fri, Mar 11, 2016 at 04:05:15PM +0200, robert wrote:
I would like to know what are the capabilities of
the silent-call
implemented in OpenBSC. When I try the command from VTY, I do not get
any useful information from the target. Should it be like a normal
call where I can listen to the called number but without having the
target notified?
a silent call is a pure signalling connection, it does not have any
actual voice data. It serves primarily the purpose of turning the MS
into a permanently (on one TS) transmitting beacon that can be localized
using various radio-localization techniques.
We implemented the feature in order to demonstrate/show-case some of the
GSM "mis-features" that are being abused by signalling intelligence /
law enforcement devices.
--
- Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/
============================================================================
"Privacy in residential applications is a desirable marketing option."
(ETSI EN 300 175-7 Ch. A6)
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robert