Windows-based Network Monitor servers require WinPcap or Npcap software.
DLP Network Monitor: 15+
Packet Capture in Windows requires software to integrate with Network Interface Cards (NICs).
Npcap is the update to WinPcap packet capture library.
You may download WinPcap software at the following URL: http://www.winpcap.org/
You may download Npcap software at the following URL:http://nmap.org/npca, however, Symantec recommends using the bundled version of Npcap over WinPcap, provided with Symantec DLP Network Monitor.
Npcap is included with the DLP Platform installer within the Third_Party folder and is for Windows only, For example, Npcap version 1.10 can be found in the following path: DLP\Symantec_DLP_15.8_Platform_Win-IN_15.8.00000.19012\New_Installs\Third_Party\npcap-1.10-oem.exe
NOTE: Either Npcap, or WinPcap, is required if you are using the Napatech NICs to capture traffic on Windows-based Network Monitor Servers.
Refer to:
15.8 Required third-party software
16.0 Required third-party software
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Article Id: 159896 When is the Npcap and WinPCAP software used in DLP?