The easiest is to search for those files in GUI and delete the found files. Note the Delete button on Find dialog:
https://beta.winscp.net/eng/docs/ui_find

We recently got hit with a SamSam attack and have a bunch of unwanted files on Box. How would I recursivly delete all files that have these two "Sorry-for-files.html" and "._weapologize" in there file name. Right now, I am actively scanning for "*Sorry*" files, but I believe scripting it would be better. Thank you for your assistance.