Digging into the Sophos log, I find the following:
com.sophos.intercheck: Encrypted file: /Registration List.xlsx com.sophos.intercheck: Corrupt file: com.sophos.intercheck: Corrupt file: com.sophos.intercheck: Corrupt file: /MRJPlugin.jar com.sophos.intercheck: Corrupt file: /MRJPlugin.jar com.sophos.intercheck: Encrypted file: /Registration List.xlsx com.sophos.intercheck: Corrupt file: com.sophos.intercheck: Corrupt file: com.sophos.intercheck: Encrypted file: /Registration List.xlsx com.sophos.intercheck: Corrupt file: com.sophos.intercheck: Corrupt file: /MRJPlugin.jar
The MRJPlugins are archived from 2002 and 2003 and no longer used--I don't think they're a threat. Besides, I've been running Sophos AV for over a year, and I've never had a whisper of a problem. Why now?
Any advice on finding the problematic files and removing them would be helpful, as would an explanation of the Mal/Phish-A threat.
I once got an alert in the quarantine manager and after some digging it turned out to be an spam email (in the spam folder) of Mac Mail. It kept coming back when I accessed the email.
You should clear the alert and rescan - no point spending a lot of time looking for something that isn't there.
If the alert comes back and you cannot see the source I'd run the SDU log gathering tool (Mac version) on your computer and raise a ticket with Support.
SDU: Sophos Diagnostic Utility (SDU): how to download and install
Raise a ticket (ensure you include the SDU output): Support query form