The LAN or PC is simply connected all the time. This means that anyone anywhere in the world could potentially ping their LAN or PC, and if they wish, play all kinds of havoc. Who knows, but in these days of schoolyard shootings, it is certainly within the realm of possibility for malcontents to intentionally damage your intellectual property. End-users do not know how truly vulnerable they are it is up to you as their professional provider to tell them. Residential users to corporate networks they all are vulnerable and need your help in protecting themselves.
Few people leave their houses unlocked or their cars running with the keys in the ignition anymore.
Leaving a dedicated connection to the Internet unsecured is tantamount to the same. Depending on the scale of what you wish to protect, your methods will be very different. For single PCs or small LANs, simple software protection is normally sufficient. This type of software includes rule base functionality that will employ time of day or day of week restrictions that the user establishes. It s cheap and reasonably effective.