But all codes are eventually suceptible to brute force attacks.You mean ciphers not codes. The point of cryptography is to make the expense of breaking the cipher greater than the amount of time the data has to be kept secret. For example the message "The suicide bombing starts in two hours Abdul" doesn't need to be kept secret as would a message planning something six months in the future.
Exactly. Encryption more often works by making the information stale by the time an adversary cracks it. This is seen in the VENONA messages Doctor Stochastic mentioned earlier. The Soviets were using one time pads to encrypt their messages. When they did it properly, it made the transmissions virtually impossible to read. But there were sometimes errors in the handling of the code sheets. This allowed the US and the UK to eventually read some of the messages, though years later. The content of any given message was, of course, beyond stale; but, there were some items that weren't out of date. The Soviets, thinking that the code was unbreakable, used the same covernames for years. Traffic analysis and the like allowed the US and UK to identify many of the Soviet agents mentioned.
That information hadn't gone stale by the time the messages were cracked! Among the agents who's codenames were uncovered were Julius and Ethel Rosenberg.
The NSA's VENONA pages are a facinating read.