Block the protocol in Ubuntu

[Riley01]

I have a assembled desktop system with Intel dual core processor, 2GB of RAM and 500GB of hard disk. I use 2 operating systems, one is Windows xp and the other one is Ubuntu. Since I am in marketing field , I have activated unlimited internet plan to research on the current market scenario and to gain frequent mail access. But these days there is a risk of lot of spams, I have heard that it can be done by blocking the protocols. Is it possible to block the protocol in Ubuntu?

[Dr. V]

You can do this if you have two LAN cards installed in your system. If you have a server system , you can use one card to interact with the clients that are connected to the server and the other card to access the internet. So you can block your address space by blockin your IP address i.e drop the variable of from the iptable. If you are unable to block the UDP protocol then change the UDP protocol and and try to block the ICMP protocol.

[Calvin K]

Iptable is an application program for the user space ,through which the administrator configures the table that are being provided by the kernel of the Linux. It generally stores ipchains and rules and these chains and rules vary from the protocol being used. The older version of the Ipv4 use itables, ip6 tables for IPv6 but I do not have any idea about the kernel module being used for the UDP protocol. If you want to block any protocol you can set the rules for the the respective protocol and block the protocol which is not desired.

[MrChris-]

You can play with the iptable i.e do a lot of things with the iptable that includes blocking as well. But you cannot delete the 3 built in chains INPUT, OUTPUT and FORWARD. You can do a lot of operations to handle the ipchain.You can create a whole new chain and delete a chain if it is empty. The rules in the chain can be appended, inserted and even replaced with some other rule. By append we mean it is added at the end of the the chain and Insert mean to add the rule in between irrespective of the sequence.

[Lillebror]

You can change the client settings and drop the incoming UDP packets by blocking the ports . I know that the UDP protocol can be blocked using the iptables. The incoming packets will be waited in a queue and matched with the iptables and it's rules, if it fits with the rules then only the packet will be accepted otherwise the packet will be dropped.But this address blocking is a simpler task in Windows operating systems than any other O/s . And you already have windows O/s in your system ,So I would prefer you to do it in Windows if I would have been in your place.

[jesse]

We just assume a scenario that you have a router that has an IP address 192.168.1.100. As you you do not want to control the outgoing of the packets so there will not be any forwarding rule. You want to block the incoming packets. Consider -A INPUT -s 192.168.1.0/255.255.255.0 -p UDP -j DROP in the iptable. One of our friend suggested to use the ICMP protocol. I think you should not do it because using the ICMP protocol each and every IPaddress will be blocked.You can also block. Suppose you want to block the downloading from the Torrent then you can simply make changes in the torrent client settings and stop the downloading