A network technician is investigating a sudden decrease in network performance at a client's office. Upon initial examination, the technician notices that the issues started right after the security team performed an upgrade on the firewall. Users report slow internet speeds and intermittent disconnections. Based on this scenario, what should the technician consider as the probable cause of the network performance issues?
Malfunctioning server within the client's local data center
ISP outage affecting external network access
Misconfiguration or an issue resulting from the recent firewall upgrade
A physical break in the main fiber optic cable serving the office