Facebooks new security

I have not seen that behavior at all. I have about 6 different computers that I access my Facebook account from at any time, and none of them have ever displayed any warnings, much less asked me to scan my account. I would be a little concerned that you might have some sort of malware on your computer, since "scanning" Facebook would require you to scan something that resides on a remote server, that you don't have administrator rights to. In fact firewalls block attempts to scan a computer from a remote source, that's why you have to grant permissions for even web based virus scans to run on your own machine.