I'm new to IPTables and am setting it up on my Linux box. As I read more on it I'm getting confused about the basic operation. Most of the rule sets I've examined have the following three lines at the top
followed by various other rules also with lines that ACCEPT. I am guessing I'm missing something basic here. I would think that the first lines should be all DENY and then specific ACCEPT lines. The basic premise would be to deny eveything and then open holes as necessary. What am I missing, why aren't the first three lines like bellow?
Thank you for any help.