Customers with some of the UK's leading internet service providers (ISP) have been alerted to a phishing scam.
Customers of BT, TalkTalk, Sky Broadband and PlusNet have been told to be vigilant for fake pop-up messages purporting to be from these organisations.
ISPs do not typically adopt this approach to share information with their customers, particularly as many people use ad blockers to stop such messages appearing.
However, ISPreview.co.uk reports that fraudsters are placing adverts on trusted websites that are infected with a "bad" pixel, which can redirect users and plan malware on their device, even if they do not click on the ad.
The malware then opens an invisible website that acquires IP addresses, which in turn enables fraudsters to identify which ISP customers are with.
Targets will then be presented with a pop-up message that appears to be from their ISP that warns them about a danger on their computer and urges them to ring a support number.
BT has urged its customers to be very mindful when it comes to maintaining their online security.
"Our advice is that customers should never share their BT account number with anyone and should always shred bills," a spokesperson commented.
"Be wary of calls or emails you’re not expecting. Even if someone quotes your BT account number, you shouldn’t trust them with your personal information.”