A security analyst notices a number of SIEM events that show the following activity: Which of the following response actions should the analyst take first?

Disabling powershell.exe on all endpoints is a broad containment measure that might disrupt legitimate operations and should not be the first response unless PowerShell is confirmed as the primary vector for the specific observed activity.

Restarting Microsoft Windows Defender would not immediately resolve an ongoing communication to a malicious IP, as it primarily deals with local endpoint protection and detection, not network-level blocking of external IPs.

If SIEM events show suspicious communication with the IP address 40.90.23.154, configuring the forward proxy to block this IP is the most immediate and effective first response action to contain the threat by preventing further outbound communication to a potentially malicious command-and-control server or data exfiltration point.

Disabling local administrator privileges is a general hardening measure, not an immediate first response to stop ongoing malicious network communication observed in SIEM events.