00000000FF FF FF FF 0D 0A 1A 0A  00 00 00 0D 49 48 44 52|............IHDR|

A file is named secret.png but Windows refuses to open it. What's the immediate problem?

• 1Nothing — PNG headers vary
• 2The PNG magic should be 89 50 4E 47 0D 0A 1A 0A. Here the first 4 bytes are corrupted — restore them to 89 50 4E 47 and the file opens
• 3It is not a PNG at all; it is a PDF
• 4The file is encrypted with AES