Thanks for that bosco555
However, this is really an issue for the anti-virus applications users run on their workstations, not SME.
SME has clamav, which scans files stored on the server (or so I believe).
The ransomware style of virus does its dirty work when you open your email - on your PC, or Mac or whatever, not on the SME.
So, the solution is to have good, up-to-date AV software running on your workstation, one that monitors in real-time. And preferably one that an monitor in webmail and attachments.
It was a timely reminder that we all need to be careful.
Cheers
Ian