A Final Thought

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Every client connecting to the Internet is a potential point of attack because with the TCP/IP protocol suite all clients are also servers and can therefore accept connections from remote hosts. A neighbor of one of the authors saw the following on his screen (please pardon the atrocious spelling) and asked the author what had happened:

Your computer is vonrable to hackers please add passowrd to your sharring acounts! If you dont do that people can conect to your computer and deleate everything on your hard drive or put a virus in your comput. mayby evan a trojan and after that he can furthur exploit your computer. so plz plz set up a password...

No damage was dome by me!

The attacker had connected to the server using NetBIOS, set the file containing this text in the Startup group, and remotely rebooted the computer! You can easily fix the problem by unbinding NetBIOS and/or adding passwords to any shares. Be especially careful of client computers that use DSL or cable modems, which are always connected to the Internet.

The lesson is a simple one: secure every computer connected to the Internet.