A clever scam

I was contacted last week by a caller purporting to be from BT. The gist of his "pitch" was that my router was being used by some outside, non-authorised users, who were effectively reducing my broadband speed.
He said that I needed to "block" these users.

I began to get suspicious when he seemed unable or unwilling to confirm whom he thought he was talking to, so I refused to do anything until contacted formally by BT.

At this point he told me that he, acting on BT's behalf, would have to cut off my internet connection (ouch!!) unless I cooperated and it would take several weeks and a significant payment to get it back again.

At this point I terminated the call and subsequently confirmed with BT (who dealt with my call very efficiently) that it was all a scam, and that BT would never contact users in this way.

Which left me wondering how the scammer was going to make money out of it even if I had gone along with the process.

BUT – and this is the clever bit to watch out for – at one point he wanted to convince me that he knew it was my own specific computer he was talking about, and he did this by asking me to look at one of the Windows 10 files which contain a lot of convincing numbers in a mixture of numerals and letters (what we computer nerds usually call HEX), which he read off to "prove" that he knew the serial number of my computer.

A subsequent check with Julian at TechMedia confirmed that this is fact a standard number, common to all Windows machines. But at the time it was pretty convincing and disconcerting.