Ming
That's strange. The NIC should only switch the PC on if it receives a message to it's specific IP. Your router or more likely one of the other PCs on the network is probably polling the network to see who is connected.
I beleive that can be disabled but it makes life ugly. Some machines may not see each other on the network when they have been switched off for a while.
OH! Or if there are open ports on the router you may be getting ping attacked by your ISP or hackers. I get a lot of traffic through open ports, a lot of it from my ISP.
WOL does not work using IP addresses. So it does not matter if a machine on the local network is "polling" the network to see who is connected. Wake on Lan does not need to be enabled and won't make life ugly in any way shape or form. Wake on Lan has nothing to do with connectivity.
Open ports or ping replies even from the outside on open ports that are forwarded to an IP won't have any effect. Since the computer is turned off, the IP is not available in the local network, as no machine is going to be there to reply to an arp request which the router will send before trying to send the packet to the machine, so essentially all that traffic get's dropped on the ground.
There is no reason for your ISP to be checking open ports, unless they are scanning for known vulnerabilities.
Wake on Lan is a special packet that gets sent on port 0/7/9/40000 (40000 is used by newer Intel cards). The packet is UDP and is sent on the IP address 255.255.255.255 (broadcast) which means every machine plugged in will get this packet at it's network interface, as the switch/router will forward it to every port that is currently turned on (Wake on Lan only works if you see blinking lights on the back of your NIC when your computer is in soft-off state).
The packet then contains the information on what Mac Address it wants to wake up, and a possible password.
Code:
ffffffffffff[macaddr x 16]
is what the packet looks like, for a PC with mac address 00:11:22:33:44:55
the packet would look like this:
Code:
ffffffffffff001122334455001122334455001122334455
00112233445500112233445500112233445500112233
44550011223344550011223344550011223344550011
22334455001122334455001122334455001122334455
001122334455001122334455
Now if that machine needed a wake on lan password, you replace the last mac address with the password.
Code:
ffffffffffff001122334455001122334455001122334455
00112233445500112233445500112233445500112233
44550011223344550011223344550011223344550011
22334455001122334455001122334455001122334455
001122334455WAKEUP
Now, I know this is over most people's heads, however I just wanted to point out that any traffic on the local network does not matter, it requires a very specific packet. A router or switch WILL not automatically send these packets.
Before making claims that something is going to be ugly, please read up on how it really works.