A proxy server sits between a client and the internet, forwarding requests on behalf of the client. It can inspect, filter, log, and cache web traffic.
How it works
- Client sends web request to the proxy (not directly to the internet)
- Proxy inspects the request (checks category, user, policy)
- If allowed, proxy forwards it to the destination
- Response comes back through the proxy to the client
Common proxy behaviours
| Scenario | What happens |
|---|---|
| URL has no category | Hits implicit deny (Bluecoat behaviour) |
| User not authenticated | Returns HTTP 407 Proxy Auth Required |
| Site blocked by policy | Returns a block/exception page |
| Site whitelisted | Bypasses filtering |
Authentication
Proxies often use BCAAA (Blue Coat Authentication and Authorization Agent) to authenticate users against Active Directory before allowing traffic.
Flow: Client → Proxy → BCAAA → AD → Proxy → Internet
Related Notes
- Bluecoat - Error Status code 407
- BlueCoat - Denied no category
- Bluecoat - Generate Proxy Trace
- Bluecoat - ExceptionBlock Pages