In the course of responding to a security breach, Rupert uncovers that an intruder who had control of a workstation at his organization's headquarters sent Social Security numbers (SSNs) via email in a spreadsheet. Rupert intends to avert further SSNs from being sent from his system while maintaining operations as usual. What type of mitigation strategy will BEST accomplish this goal?

A data loss prevention (DLP) tool that can analyze and inspect emails for SSN-like data is the most efficient tool mentioned in this scenario. Rupert might prefer to configure the tool to impede all emails containing potential SSNs and then check those emails manually to guarantee that no more emails are sent while allowing authorized emails to be delivered. Although an intrusion detection system (IDS) may seem like a feasible solution, it can only identify traffic and cannot prevent it from leaving the organization, which would allow the SSNs to be exposed. Antimalware and firewalls cannot prevent such events from happening.