This bug-eating add-on was completely free, blown my way by the wind. You can, of course, opt for the paid versions of the well-known anti-virus programmes. But
Windows Defender, included free of charge with the Microsoft operating system, already delivers excellent performance for the average user. On the odd occasion it fails however. By successively running a number of other programmes on my laptop, I eventually managed, through trial and error, to track down the culprit: a very clever Trojan.
But even in such cases, the free versions of a number of excellent anti-virus programmes usually offer a suitable solution.
Line up the usual suspects.