You want to block incoming traffic from a particular host.
To block all access by that host:
For iptables:
# iptables -A INPUT -s remote_IP_address -j REJECT
For ipchains:
# ipchains -A input -s remote_IP_address -j REJECT
To block requests for one particular service, say, the SMTP mail service:
For iptables:
# iptables -A INPUT -p tcp -s remote_IP_address --dport smtp -j REJECT
For ipchains:
# ipchains -A input -p tcp -s remote_IP_address --dport smtp -j REJECT
To admit some hosts but block all others:
For iptables :
# iptables -A INPUT -s IP_address_1 [-p protocol --dport service] -j ACCEPT # iptables -A INPUT -s IP_address_2 [-p protocol --dport service] -j ACCEPT # iptables -A INPUT -s IP_address_3 [-p protocol --dport service] -j ACCEPT # iptables -A INPUT [-p protocol --dport service] -j REJECT
For ipchains:
# ipchains -A input -s IP_address_1 [-p protocol --dport service] -j ACCEPT # ipchains -A input -s IP_address_2 [-p protocol --dport service] -j ACCEPT # ipchains -A input -s IP_address_3 [-p protocol --dport service] -j ACCEPT # ipchains -A input [-p protocol --dport service] -j REJECT
You can also block access at other levels such as TCP-wrappers. [Recipe 3.9][Recipe 3.11]
iptables(8), ipchains(8).