Apple has released an update to the iPhone which fixes a massive SMS exploit. The update weighs in at 280 MB.Apple’s knowledge base article details what the massive update fixes:

Impact: Receiving a maliciously crafted SMS message may lead to an unexpected service interruption or arbitrary code execution

Description: A memory corruption issue exists in the decoding of SMS messages. Receiving a maliciously crafted SMS message may lead to an unexpected service interruption or arbitrary code execution. This update addresses the issue through improved error handling. Credit to Charlie Miller of Independent Security Evaluators, and Collin Mulliner of Fraunhofer SIT for reporting this issue.