Complex sentence: The virus, which originally targeted Symbian Series 60 smart phones, failed to cause an epidemic, but its ability to propagate via Multimedia Messaging Service messages (MMS) worried some experts at the time of its discovery.
Split into simpler sentences: The virus, originally targeted at Symbian Series 60 smart phones, failed to result in an epidemic. However, its ability to propagate via Multimedia Messaging Service messages (MMS) worried some experts at the time of its discovery.