full-disclosure - GPRS/IP-session from Nokia/Symbian mobile phone stays up

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From: mdavids at forfun.net (Marco Davids (Prive))
Subject: GPRS/IP-session from Nokia/Symbian mobile phone stays up

Hi,

For what it is worth:

When my Nokia 6600 (Symbian V7.0s) mobile phone was connected to the
Internet and an imap-server for some tests the other day, I decided to
run a ping to the phone's IP-address (in fact I did an nmap -O to the
phone first, but that didn't work).

After the mail was retrieved I closed the email-application on the phone.
Normally the GPRS-session is terminated in such a case. But not this time,
while the pings went on. This time I had to force the session to go down,
which is an option on the phone, luckily. I just never used it before :-)

Later on I tried an SSH-session with the Mocha Telnet application from my
phone. Same behaviour. After I closed the SSH-application and as the
pings went on the (expensive) GPRS-session did not terminate as it
normally does when there is no incoming icmp traffic. When I finished
the external pings to the phone, the GPRS-session closed by itself.

I tried again, this time with a larger packet-size, but that did not work.

Then I tried a flood-ping and that did work. The GPRS-session stayed up
and the GRPS-counters increased dramatically! By this time my little
experiments where getting rather pricey for me.

Conclusion: Even after the last application that uses IP on the phone is
closed, the GPRS-session stays up as long as there is incoming
(icmp)traffic. I am not sure what to think of this, but this seems
rather undesirable to me. Do other phones also 'suffer' form this
behaviour?

This 'feature' can be abused. One could easily be lead to believe that the
GPRS-session is over, while in reality it is not.

I did a quick ping-scan on the IP-range that my phone was in and
discovered 355 active, 'pingable', IP-addresses out of 2048. I figured it
be better not to start flood-pinging all of them them, but I couldn't help
thinking what would happen if some punk did: many phone's online would
probably stay online, depending on the number of phone models that show
the same behaviour. That would not only generate costs to their owners,
but would probaly also exhaust available IP-addresses for new
connections, resulting in some kind of DoS to the GPRS IP-service.

Greetings,

--
Marco Davids