Hello,
This Option would Let Symantec Endpoint Protection use Symantec's reputation database to make decisions about threats. The reputation database is called Symantec Insight. Queries to the database are called Insight lookups.
Download Insight, Insight Lookup, and SONAR use Insight lookups for threat detection. Symantec recommends that you allow Insight lookups if possible. Disabling Insight lookups disables Download Insight and may impair the functionality of SONAR and Insight Lookup.
However, you can disable this option if you do not want to allow Symantec to query Symantec Insight. For example, your company may require you to turn off external communications with the network so that data never leaves the client.
This option is enabled by default.