VBS/Agent.PDB!dam is a generic detection for a damaged version of VBS/Agent.PDB!tr.dldr.
Some samples of VBS/Agent.PDB!tr.dldr were found to be 7zip but the latest ones were damaged Rar archives and has been flagged as VBS/Agent.PDB!dam.
The samples appear to have been concatenated from the bottom part of the file.
- Make sure that your FortiGate/FortiClient system is using the latest AV database.
- Quarantine/delete files that are detected and replace infected files with clean backup copies.