Understanding Content Filtering Protocol Support
Each supported protocol may implement available content filters differently. Not all filtering capabilities are supported for each protocol.
This topic contains the following sections:
HTTP Support
The HTTP protocol supports all content filtering features. With HTTP, the content filter remains in the gateway, checking every request and response between the HTTP client and server.
If an HTTP request is dropped due to content filtering, the client receives a response such as:
Therefore, a message may appear as follows:
FTP Support
The FTP protocol does not support all content filtering features. It supports only the following: Block Extension List and Protocol Command Block List.
When content filtering blocks an FTP request, the following response is sent through the control channel:
Therefore, a message may appear as follows:
E-Mail Support
E-mail protocols (SMTP, IMAP, POP3) have limited content filtering support for the following features: Block Extension List, Protocol Command Block List, and MIME Pattern Filtering. Support is limited for e-mail protocols for the following reasons:
- The content filter scans only one level of an e-mail header. Therefore recursive e-mail headers and encrypted attachments are not scanned.
- If an entire e-mail is MIME encoded, the content filter can only scan for the MIME type.
- If any part of an e-mail is blocked due to content filtering, the original e-mail is dropped and replaced by a text file with an explanation for why the e-mail was blocked.
Related Topics
JUNOS Software Feature Support Reference for SRX Series and J Series Devices