The (CTD) Content-Based Threat Detection engine used by a multitude of Palo Alto
Networks platforms now provides support for Brotli decompression for improved
analysis and threat detection of HTTP content. Brotli is a high-efficiency data
compression format with widespread support that was developed by Google for HTTP web
applications and content. Palo Alto Networks Security subscription services, such as
Advanced Threat Prevention, Advanced WildFire Advanced URL Filtering, and others
rely on the CTD engine to facilitate traffic inspection. With the addition of the
Brotli decoder, traffic that was previously dropped, or is otherwise passed through
the network as an unsupported content-encoding type, is now processed and available
for inspection by various Palo Alto Networks content inspection features. This
includes, but is not limited to Precision AI™ optimized features such as
Advanced WildFire: Inline Cloud Analysis,
Advanced Threat Prevention: Inline Cloud
Analysis, and
Inline Deep Learning Analysis for Advanced URL
Filtering; but also includes any HTTP traffic payloads processed by a
configured and enabled security policy. This allows for broader visibility into
traffic and helps protect against attackers using Brotli compression to bypass
traditional security mechanisms. When
enabled, this software-based Brotli
library is integrated into the existing content decoder framework. Due to the
expected increases in traffic inspection, the firewall requires additional resources
to enable the feature; and as a result, is only available on select platforms.