0 0 saga1086 xantos 46000 ESTABLISHED tcp 0 0 saga1023 anyonuionologin

0 0 saga1086 xantos 46000 established tcp 0 0

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0 0 saga.1086 xantos-4.6000 ESTABLISHED tcp 0 0 saga.1023 anyon.uio.no.login ESTABLISHED tcp 0 0 saga.1080 xantos-4.6000 ESTABLISHED This gives an indication of who is currently connected. Of course, intruders could connect when you are not watching, so another thing to do is to monitor all the connections made to your machine continuously and dump the result to a file. This requires a considerable amount of storage and some skill in interpreting the data. The program tcpdump will do this. Sun have their own version called etherfind . On the other hand, we cannot live in a perpetual state of paranoia, thinking that everyone is out to get us. A balance must be struck by taking all reasonable precautions and being aware of the problem . Finally, the super-user should never install software which is of suspicious or unknown origin. 8.6 Firewall One way of designing a network to protect it from attack is to use a machine as a ``firewall''. That is - a barrier to stop the spread of network threats. The idea is to isolate important machines by placing another highly secure machine between the outside world and the local network. The firewall is the only machine which is connected to a wide area network. It is also connected to the local area network, but it does not forward packets to the local network and vice versa. Thus sensitive data can be hidden behind the firewall, where they can be shared on the local network but not by the external network. 8.7 Public and Private Keys A clever intruder could always behave as an imposter - arranging it so that it appeared that a network request came from a trusted machine, when in fact it came from the intruder's machine. Moreover, one could easily make a device which collected all the information which was sent over a network and analyzed it to find out what was being said - and to whom. To try to prevent such problems from occurring, we can use a system of data encryption (coding). The idea is to encode all data using a special key. Both the sender and the receiver need to know the key - the encryption and decryption algorithms are publicly known. The problem is then to agree on a key. This can be achieved using public and private keys . Two parties wish to communicate with one another in private, so they encrypt the data they send over the network. Each host has a private key which is a large number which is encrypted with the user's password and stored in a database. Each user also has a public key, which anyone can look up in a database. In order to exchange information, both the sender and the receiver need to have the correct key. The ingeneous part is that, both parties combine their private keys with the others' public keys and end up with a conversation key which they both agree on. To decode a message they only need the conversation key and their own private key. The coding algorithm is based on some inspired mathematics of modulo arithmetic.
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