Hello,

I have configured firewalld to zone drop. I need to know whether i should add rules to block syn,xmas,null packets or not,because i have already set to drop zone.

Thank in advance.

Your question should have started by doing researching into what the characteristics are of Null and X-Mas scans. Then you should have asked yourself (or even prove empirically by watching traffic) if there are situations where traffic legitimately has no (Null) or all (X-Mas) flags set on packets. The other thing to research is the "new not SYN" situation (not sure how one would get to that themselves except for encountering it or reading much). Finally you can (log and) test if Netfilter already drops everything when "-j DROP" rules are used, is your answer.