Mobile Security Lab

UDP/9204 is associated with the service WAP-vCard and is used for sending vCard files to the device, that are displayed as normal SMS to users.
By flooding the device with multiple vCards it is possible to perform a Denial of Service attack that affects usability, SMS handling and connectivity.
By sending large number of vCards an attacker can achieve significant device slowdown, making the UI sluggish and hard to use.
In some cases WiFi connections may be dropped (when vCards are sent via WiFi), effectively disconnecting the device from the network.

On Touch Cruise devices, SMS inbox can be completely filled by sending more then 450 large vCards (size 32K).
The device will not be able to receive SMS anymore or to access the message stored inside the device until SMS deletion occurs.
Additionally, when large vCards are sent, no acoustic notification (ring tones) will be played upon incoming messages, making the attack more silent and less noticeable by an user.

Battery removal may be needed, in some cases, for restoring normal functionalities.
Manual deletion of all received SMS requires a very long time, making the deletion of all the SMS the most viable option, but leading to loss of all received SMS and requiring in any case a large amount of time (even hours).
The faster option for restoring the device is performing a hard reset of the device, leading to the loss of all the content saved on the handset.

The attack can be easily carried in all the scenarios where the device IP stack is accessible to an attacker, such as Wireless LANs and Mobile Networks assigning public IP addresses without any firewall protection.