Introduction¶
Operational frontends serve as critical filtering layers that blend malicious traffic with legitimate services to evade detection. These systems implement sophisticated content-based routing to distinguish between benign web requests and callback traffic from compromised systems. Proper frontend configuration can defeat simple signature-based detection while providing operational flexibility through features like domain fronting and protocol impersonation - all while maintaining plausible deniability through carefully crafted cover content.
Why?¶
The frontend initiates connections to the target, scans machines, and routes incoming packets from a reverse shell through a web proxy to deliver them to a backend systems, a C2 framework like Metasploit or SilentTrinity.
This packet routing can be done with a regular web proxy like Nginx or Apache that acts as a filter: requests from infected computers are routed to the corresponding backend C2, while the remaining requests are displayed an innocent web page.
It must be unique to each operation or target, and be quickly replacable every few days.
How?¶
The Nginx web server can be tuned relatively quickly.