This is a small application built to demo the weakness in pgsql and networking. It is capable of running login attempts from multiple threads in parallel and can run up to 1024 concurrent connections.
You can download it from the following link: https://packetstormsecurity.com/files/download/109279/brute-pgsql-2012-01-30.c
Source: https://packetstormsecurity.com/files/109279/PgSql-Brute-Force.html