Can downloaded executables get my MAC address and send it to somewhere else? Also, why is it a security risk to have someone else use my MAC address, considering that it can be spoofed?
Yes, software running on your computer can find your MAC address. If you have a malware infection, your MAC address leaking is probably not greatest of your worries (keystroke loggers, and RAM scrapers, and backdoors are a lot bigger worries).
In general your MAC address isn't really secret (it is sent with every ethernet frame), but it could potentially be used for a couple of things:
- If your network relies on a MAC address whitelist (only allowing computers with MACs on the list to join) an attacker could use your MAC address to get onto your network. (An attacker who is specifically targeting your organization is your threat here)
- The MAC address of your Wireless networking card can be used to track you. If a malicious entity knew which MAC address belongs to you, they could potentially follow you around by your phones/laptops wifi signals. (Here the threat is a very creepy stalker)
- A MAC address identifies your network card. Potentially, an attacker with lots of resources may be able to track which computer your particular networking card was installed into, and then find out who bought that particular computer. (Something to worry about if the government is after you)
I think there's a massive misundestanding about what a MAC Address is.
Nobody should get worried about MAC address. Period. Unless the attacker is in the same physical network segment than you, a MAC is useless. MAC address never leave the local network, they are easily changed, faked or cloned, they are not unique even if they were meant to be (there are stories of people with duplicate MAC addresses on they networks), and if the government wants to identify you, your browser if orders of magnitude easier than the MAC. They can hack your computer outright, and get everything. MAC won't change a thing.
So don't bother thinking about the MAC.
Now, the questions:
Viruses getting my MAC:
Yes, it's possible. The
getmac command on Windows or
ifconfig on Linux can get it. Any program can execute the same and get your MAC. Any program can transmit it over the Internet.
It's a security risk?
No, it's not. A virus infecting your computer is a security problem. If some unknown program is reading your MAC, the program is the problem, not what the information it reads.
What if someone else uses it?
Unless they are on the same network segment than you, nothing happens. If your network card is a cheap Chinese board, at least one thousand computers are using the exact same MAC as you, right now.