According to the mobile communications expert Tobias Engel, a number of Nokia phones and E90 Communicator among them, are vulnerable to Denial of Service (DoS) attacks. Interestingly, no special software is required to exploit this vulnerability. If an attacker knows the text that exploits the vulnerability, she can cause serious damage to your phone. After the attack, the phone does not accept SMS/MMS anymore and the only solution is a hard-reset or in the worst case rewriting the firmware.
Via SecuObs.com