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Isolated SentinelOne Agent Will Not Reconnect to Management (Reconnect Manually)

  • Updated .

Issue

The SentinelOne Agent was placed into isolation, but it is not able to be reconnected to the SentinelOne Server (Management).  How do I remove network quarantine (isolation) manually from an endpoint with the SentinelOne agent installed?

Environment

SentinelOne

Resolution

In order to restore network connectivity please follow these steps: 

  • Get the passphrase of the Agent (someone with Admin rights in the S1 portal will need to retrieve the Agent passphrase).

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  • Run unquarantine_net commands:

For Windows:

  • Open the Command Prompt and Run as administrator.
  • Go to the folder that contains SentinelCtl.exe:
cd "C:\Program Files\SentinelOne\<Sentinel Agent version>"
sentinelctl unprotect -b -k "<passphrase>" 
sentinelctl unquarantine_net 
sentinelctl protect

For macOS:

sudo sentinelctl unprotect -k "<passphrase>"
sudo sentinelctl set allow-network
sudo sentinelctl protect

 

Additional Troubleshooting (Windows):

If you cannot get the passphrase for the Agent, or these steps do not work, you can reconnect the endpoint from the registry.

  1. Open regedit.exe as Admin on the endpoint.
  2. Go to:  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\BFE\Parameters\Policy\Persistent\SubLayer
  3. Delete this key:  1F3649F2-1FB2-443E-8152-C209804E2A4F
  4. Reboot the endpoint.

Cause

This can happen for a variety of reasons.  One example is a race condition where the S1 Agent does not recognize that it has been placed in isolation.  Another example is a corrupted S1 Agent installation, or DNS resolution errors.