Wow, we live in a completely Internet ran world now and this should be more second hand then a question. Anything ran on line and sent over the Internet is sent by a code. Anyone with half a brain can write a code, but real malicious people can have true mastery in setting up an exe in anything. and to answer the question, a .swf is no more safe then any other file format. So if your unsure about things, think about this. Look at the file size if your looking at a image and its going into the MB's there is something fishy unless its huge at like 600DPI, but its common sense in things like this, if your not sure about things scan everything or enjoy having a 3,000 paper weight on your desk.
COME ON PEOPLE THIS IS COMMON SENSE!
having cleaned too many friends computers from stupid things they have downloaded and sites they have visited. And all you porn dogs.. your the biggest target .. you think those sites are clean? heh.. yeah..