|I've had AVG8.5 freebie pick them up online with a big red warning, many times.|
I always heed the warning of-course but I wonder if your clients don't opt away smartish. They need to know about Alt+F4 keys because with much of this sort of crap 'No' often means 'Yes' so you have clear the offending screen pronto, without clicking the mouse on it.
I don't know the answer to your question. Maybe they are popping up all over the place before they get noticed and databases can't get updated in time. From what I've read Microsoft Security Essentials (also free) is "supposed" to detect them so it might be worth a thought.
some other bloke...