firewall just ignore the rule

[liyas_m m <liyasmm@xxxxxxxxx>]

I hv iptables 1.2.7 installed on my firewall
The problem is  when i try to block traffic from certain address , it
just does not work
e.g
iptables -A INPUT -s 10.5.33.22 -j DROP

but when i run iptraf , there are still traffic sent from the source address
Any idea why?