Virgin Media has urged customers to change the passwords on their Super Hub 2 routers after Which? said they could be vulnerable to hackers.
The consumer group found that the devices could be hacked in a matter of days if they are left with the default password that comes with them.
This means that hackers could potentially gain access to other devices inside the home that run on the same network.
Virgin Media has therefore contacted 800,000 of its customers who use SuperHub 2 routers and encouraged them to change their passwords.
"The security of our network and of our customers is of paramount importance to us," a Virgin Media spokesperson commented.
"We continually upgrade our systems and equipment to ensure that we meet all current industry standards.
"To the extent that technology allows this to be done, we regularly support our customers through advice, firmware and software updates, and offer them the chance to upgrade to a Hub 3.0 which contains additional security provisions."
Virgin Media customers can change their Super Hub 2 password by connecting their computer to the device with an ethernet cable.
They can then enter the web address on the Super Hub sticker to access the settings page and click on Wireless Network Settings.
Users should then enter their new password into the box marked 'passphrase", before restarting all devices connected to the Super Hub and entering the new Wi-Fi password to get back online.
Customers can disconnect their computer from the Super Hub 2 at this point.