– Double extensions ( .avi.11.pdf ) can sometimes be used to hide executable malware. If you did not create this file yourself, avoid opening it directly. Scan it with an antivirus or use a text editor to peek at the file header (first few bytes). A genuine PDF starts with %PDF , while a video starts with something like ... or RIFF (for AVI).

In a world where motorcycle enthusiasts were a dime a dozen, one rider stood out from the rest. His name was Axel, but his friends and fellow riders had given him a nickname that would stick: "A-Rider-Needs-No-Pants."

A PDF is a document. A portable, safe, corporate format for tax forms and textbooks. But this file is not a PDF. It is a binary, a video file, wrapped in a cheap disguise.