Help !! me .Dos and Flood attack!!

[slackman]

i install linux server (fedora core 5) and setting up as INTERNET server
and open service in list below.
1. squid ** need
2. httpd ** need
3. DNS forwaring(named.conf) **need
4. iptables **need

and setting transparent proxy to 3128 port

i have problem with user in system.i think it's virus or somebody want to annoy my system (send DOS and syn food attack to 80 port) and check proccess in "top" command (apache and squid it's very hard process) and about 5-8 hour my service it's crash (i need to reset my server every 10 hour)

help me please.!!!

[slackman]

i don't want to block some computer to DOS my server with IPTABLES -DROP or -REJECT