An organization has detected a breach that resulted in unauthorized access to its customer database. Despite efforts to isolate the infected systems, the threat actor maintains persistence in the environment. Which of the following actions would be the MOST effective next step in the recovery process?
Increase network monitoring to catch further malicious activities by the threat actor.
Re-image the infected systems to a known good state before reintegrating them back into the network environment.
Disconnect the infected systems from the network and perform a basic clean-up using antivirus software.
Apply patches to the infected systems to close the vulnerabilities exploited by the threat actor.