The system must be restarted before the update is applied, while disconnected from the network. Otherwise, if the “DoublePulsar” exploit is already present, attempting the patch process could prevent the PC from starting.
To update Windows XP:
- Download the patch tool from Microsoft and save it to your desktop:
» Go to download for Windows XP Service Pack 3
- Disconnect your PC from the network (disconnect the network cable, turn off WiFi).
- Restart the PC.
- Run the installer you saved to your desktop in step 1.
- Restart the PC to complete the patch installation process.
- Reconnect to the network.
- Run the
Avast Wi-Fi Inspectorscan ( Protection▸ Wi-Fi Inspector▸ Network Scan) to confirm that the system is no longer vulnerable.
If you are unable to install the update, the only other way to fix this vulnerability is to disable the Windows file sharing service, specifically version 1 of the SMB protocol. Note that doing so on Windows XP will render local file and printer sharing inoperable.
Refer to the following Microsoft guide to disable SMBv1: