ARP spoofing is a kind of Man-in-the-Middle (MiTM) attack and it affects the machines in the subnet.
Who will affected? Almost all. Free wifi connection even it is encrypted by WPA/WPA2. Your local network. The machines inside a subnet.
How about using SSL and SSH as well as VPNs? No, those cannot protect you from being attacked by ARP spoofing. Even a switch cannot protect you from being attacked. Please refer to this presentation.
ARP security often ignored and nobody cares about lower layer security nowadays. ARP attacks are real threat with high impact.
How can I protect myself from being attacked? Yes, you can. The following tools will alert you when the attack is taking place.
If you are Linux users, you can use ArpON. If you are Windows users, you can use XARP - Advanced ARP Spoofing Detection.
For Ubuntu or Debian users, you can install it by the instruction at ArpON on Kali Linux 1.0.9a.
If you are Mac OS X users, you can use
If you are Android users, you can use WiFi ARP Guard.
ArpON for Linux can protect you from the attacks and the others are just alert you for the attacks only.
Or, if you do not want to install the captioned software and your router can set static ARP, do it and your subnet is protected upon set.
Please note that ARP Guard for Mac OS does not do the job well. It cannot detect any ARP spoofing when I test it on Mac OS X 10.10.1.
There is another way to protect your from ARP spoofing attack if you are a Linux user and do not want to install the captioned software. You can follow the instructions in the following video which was created by xiedi01 :
Want to see a demo how ARP spoofing works? Yes, the demo is by Hak5 and it starts at 07:24 for the first demo.
The following demo is conducted under Back|Track 5 R2 by MasterButcher68.
There are some tools that make this attack automatically and the attackers requires no skill to do so. Even a script kiddies can handle it. The following is one of the tools, namely YAMAS - Yet Another Man in The Middle Automation Script.
That's all! See you.