Research group F-Secure said the exploit, dubbed the "Curse of Silence," is a denial-of-service attack that can crash the targeted phone's SMS system, but the phone retains other functionality. The exploit was found by researcher Tobias Engel, and it was made public at the Chaos Communication Congress event Monday.
"Performing the attack does not require technical expertise, and due to this, there is a risk of it becoming a nuisance," said Samu Konttinen, VP of F-Secure's mobile business unit, in a statement. "We have already provided a security update to this threat to our F-Secure Mobile Security customers."
The group said attackers can specially format an e-mail to be sent as an SMS by setting the message's Protocol Identifier to "Internet Electronic Mail." If the message contains more than 32 characters, certain S60 devices will not be able to receive other SMS or MMS messages. Depending on the handset, the exploit can damage the targeted device with a single message, F-Secure said.
The exploit can potentially affect millions of handsets, including UIQ devices and handsets running S60 2nd Edition Feature Packs 2 and 3, S60 3rd Edition, and 3rd Edition Feature Pack 1. The malicious message can be sent from almost any device capable of sending SMS as "Internet Electronic Mail."
Once infected, the phone has to be factory-reset to restore text message capabilities. F-Secure does sell mobile security products that can protect customers from this, but the company said it made Nokia and multiple GSM carriers aware of the exploit long before it was publicly disclosed.
Nokia has not responded to inquiries as of press time, but this exploit could possibly receive a patch through an over-the-air firmware update. Additionally, the exploit could be spotted and stopped at the carrier level by blocking messages with the malicious formatting.
The video below also explains the exploit.