When using TCP-Z Virtual Device Driver to automatically load itself during system startup in order to modify and patch TCP/IP concurrent half-open connection limit for higher value, the system may prompt “Fail to Load Driver” error.

The TCP Half Open Limited Patcher (TCP-Z) device driver is installed onto the system in order to hack the system tcpip.sys to patch the restriction limit of half-open incomplete outgoing TCP connection system can create at any one time. On system startup, TCP-Z driver is loaded in order to perform the patching of TCP connection limit in memory. Without the driver, user have to manually launch TCP-Z to patch the system memory with custom TCP connection limit.

Sometimes, TCP-Z virtual device driver loading will fail with the error message of “Fail to load driver”. The cause of the problem is that some security software will block and prevent the TCP-Z from loading the driver. The symptom is found to affect users of KIS 2009 (Kaspersky Internet Security 200), specifically by its firewall application rules.

To resolve and fix the driver loading failed error, user must change the KIS firewall appllication rules to grant the rights and permissions to access to TCP-Z to load the driver, or TCP-Z can be assigned into trusted group.

If the resolution above doesn’t fix the unable to load TCP-Z driver issue, the workaround is either to manually run the TCP-Z and patch the connection limit after each system reboot (the TCP connection limit is only read once after system startup, and won’t change until system is shutdown or restart), or user can opt to physically patch the tcpip.sys file. To patch the tcpip.sys file directly, use Half-Open Limit Fix.