12.07.2006
If your network is in any way connected to the internet, it is by default threatened. Script kiddies or blackhats will eventually hit your network, so keeping security in mind and being prepared is crucial.
Here is a giant chart showing some of the different angles a possible attacker may use. As you can clearly see, those aren't few.
Any sane company should test their own network to ensure it's safety, and I think this chart could be helpful in that process.
And, yes, as you may have figured: You might need some Linux-knowledge to do proper testing.