I've been working on a custom purpose-specific firewall I call K-Wall, that intercepts and blocks goldseller spam for games, using regular expressions and a lot of Unicode conversion trickery. Basically it's a firewall that adds regex filtering to game chat, and does so at the network level. (Well, network transport level.) The primary game I've been building this against? Blade and Soul. In fact, the first pack-in config file for it is for BnS.

The way it works is actually pretty simple: incoming chat packets are captured and duplicated, and chat packet contents then get some preprocessing: everything is converted to lowercase, Unicode lookalike characters and multi-char sequences are converted to their lowest-level equivalents, the Unicode Consortium's anti-spoofing "confusables" correction is applied, and finally, punctuation and whitespace are selectively stripped. ("Selectively" meaning that we don't take out $ or = or other characters goldsellers like to use, but regular players almost never use.) The remainder gets passed through up to 16 regex filters, and if there are enough matches, the packet is logged and dropped into the bit bucket. If not, the original form of the packet is passed on to the game as if nothing happened. Multiple threads handle all of this concurrently to minimize latency.

Since K-Wall is a network firewall, it is by definition NOT a "third-party tool" or cheat program. (NOTE: The way NCsoft's EULA is written, it could be argued that the EULA does not allow the use of any firewall or network security tool while the game is running, because of how vaguely written the clauses relating to interfering with the game's operation are. Naturally, this is both absurd and completely unenforceable.) It hooks to Windows' networking (specifically to the Windows Filter Platform in Vista and later), and doesn't touch the game itself. GameGuardian doesn't even know it's there. (GameGuardian was a pain in my backside as it blocks development tools, which makes debugging with BnS running a lot tougher.)

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