How do you build an irule to drop connection (without completing the handshake)

We are not using GTM nor we are using Managed DNS. We use multiple A records. When multiple A records are used the client obtains both IPs. In case of Windows, the client will start using the second IP when no SYN-ACK is received to the initial SYN request sent to the first IP. This was tested by blackholing some routes.