Akamai (NASDAQ:AKAM) is already delivering Web content. Now, it wants to protect what it delivers.

This week, the industry's top content delivery network (CDN) agreed to work with Breach Security to implement what it calls Web Application Firewall, a service that hunts for and stops malicious traffic that lives in the Web's "applications layer."

Confused yet? I've been there, Fool. In the simplest terms, the Web's applications layer is where user data travels, and where cloud computing comes to life. Each time you identify yourself to Amazon.com (NASDAQ:AMZN) for a purchase, you're in the applications layer. This is the Web at its most functional, and its most vulnerable.

Breach Security, for its part, is the lead sponsor for an open-source Web firewall project called ModSecurity. Akamai will use the project's highly developed rule set to sniff out and filter attacks. (Security systems use rules to identify when an attack is in progress.)

Whether this deal gives Akamai a competitive advantage over peers Limelight Networks (NASDAQ:LLNW) and Level 3 (NASDAQ:LVLT) isn't yet clear, but it could force them to respond by seeking partners of their own. Cisco (NASDAQ:CSCO) and McAfee (NYSE:MFE) would make for interesting candidates.

Fools may remember that it was McAfee that purchased Secure Computing last fall. Secure specializes in devices and technology for identifying and stiff-arming bad-boy traffic at the gateway, before it enters a private network. Cisco has similar capabilities built into its routers and other networking equipment.

Akamai could take this approach a step further by using its 55,000-strong global server network to choke off malicious traffic near its source. Call it the doctrine of pre-emption, gone digital.

Clients must appreciate that. The nice, smiling content delivery boy they've known has grown up to be a beefy escort with a license to kill, packing a holster full of do-you-feel-lucky-punk technology.

The Web may never be the same.