404 error while accessing SP Server Site 2013

404 error while accessing SP Server Site 2013.

This is an intermittent issue.

We recently had a crypto attack on all servers hence everything was turned off.

When everything was settled, we started the server, application pools, did IIS reset,reboot of server.

however all users are still facing issues while accessing all the sharepoint sites.

They are receiving:

Server Error in ‘/’ Application. Description: HTTP 404. The resource you are looking for (or one of its dependencies) could have been removed, had its name changed, or is temporarily unavailable. Please review the following URL and make sure that it is spelled correctly.

Can someone advise on this?

thank you