How to check if someone is using your Wi-Fi

If you think your computer is showing signs of a virus infection, checking your data usage could indicate it’s part of a botnet

If you’re paying for data coverage – or if you want to keep an eye out for any computer security issues – monitoring your data usage can be a good way to see just how many GBs your employees, flatmates or family members are chewing through. Learning about Wi-Fi security at home or in a small business is an important way to protect your connection and the things you do online from eavesdropping, hacking and freeloading neighbours.

If you think your computer is showing signs of a virus infection – general slowness or odd browser behaviour, etc – checking your data usage could indicate that it’s part of a botnet and your connection is being used to send out spam.

Ways to monitor connections

There are several options to explore:

  1. Check what tools your ISP offers. Many NZ companies allow you to login to your account online and review your data use with charts and general info on volumes of data. Don’t expect to be able to see detailed logs of what people have been downloading minute by minute.
  2. Check your Wi-Fi router and see what tools come bundled with the administrative software. Modern routers often have options for reviewing traffic and limiting or restricting connections made to it. Search for the full manual online or ask your ISP for help if they provided the hardware.
  3. Look for software to monitor your connection. This could take the form of a network monitoring firewall or stand alone tool – we’ve listed a few options below to try.

WiFi Guard
A small application that will alert you if your network is used without your knowledge and may help you work out just how many devices are using your connection.

NetWorx (Windows only)
This free tool is a good way to review internet traffic over your connection and comes bundled with a visual ‘netstat’ or network statistics tool.

Who’s On My WiFi (Free for Windows and Mac)

Download the ‘Detection Agent’ software to your computer to log network activity. The Software + Online solution lets you record more data and set up reporting and alerting functions.

More information

CERT NZ have useful online security information on a range of topics including what to do if someone is accessing information online without your authorisation.

More technical users can refer to this Lifehacker guide to mapping your network using tools like nmap and WireShark to investigate network traffic.

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