You can often see which devices are connected to your wireless modem or router by looking at Web-accessible menus within the router itself. Make sure the devices you see line up with what you expect and consider changing your network password if you see connections you can't account for.
Understanding Wireless Modems and Routers
Traditionally, a modem is a device that transforms signals designed for one network so that they can be sent over another. Different types of modems include the traditional dialup modems used to connect to the internet over phone lines, cable modems that allow you to access the internet over a cable television line and the built-in modems in your cellphone that let you access data from the device.
A router is any digital device that sends data from one computer network to another, although it doesn't necessarily have to change the format of the data is a modem does. Many modern cable and DSL modems also serve as wireless routers, connecting devices using Wi-Fi within your home or workplace to each other and to the internet. Some modems don't include wireless router capabilities, but they can be connected to a standalone wireless router.
Who's On My Wi-Fi?
If you're concerned that people or devices you didn't intend are connected to your wireless network, you can often check data stored in your wireless router to see if this is in fact the case.
Exactly how to check devices connected to a router varies from router to router. Many routers provide a special Web address you can access from a device that is on your network. You'll usually have to log in with an administrative username and password and then click something similar to "View Devices on My Wireless Network." If you don't know the username and password, check to see if default login information is written on your router itself or in the router's printed or online documentation.
Which Device Is Which
Once you log in and click through to the right page, you'll usually see a list of devices indicated by their media access control address, or MAC address, and internet protocol address, or IP address. The IP address is a numeric identifier assigned by your wireless network, and it usually won't do that much to help you identify the devices.
MAC addresses are essentially serial numbers assigned to wireless network hardware by manufacturers. Some devices shift MAC addresses over time to evade tracking, but they will still operate in ranges reserved by their manufacturers. That means that while you may not recognize the lengthy alphanumeric MAC address of your cellphone or computer, you can search online using the MAC address to see who made a particular device. That can often help you figure out which devices are your phones, computers, smart TVs, smart speakers and other hardware.
Keep in mind that the term MAC address isn't linked to Apple Mac computers.
Keeping Out Unwanted Users
If you see devices on your wireless network and you can't determine what they are or know for a fact they don't belong to you, you can take steps to keep your network secure. Set a secure, hard-to-guess password, and change it if you think it's fallen into unwanted people's hands.
Many wireless routers will also allow you to block or blacklist certain MAC addresses or create a list of allowed devices, automatically locking others out of your network. Check to see if your network has such a feature, although keep in mind it can mean an extra step if you have guests who want to use their devices on your network.
Remember that unwanted users on your network might use up your data limits, access devices and files without your permission or even use your internet connection for illegal activity.