Sorry, Mary. It's not internet providers (although they might be involved) but the local LAN/WAN network people ... those persons in charge of routers/switches and gatways/proxies of the network upon which the Moodle is hosted.
The purpose of a proxy is to be able to provide a workstation (thus user of that workstation) 'privacy' and 'protection' from malicious stuff. Work with a school district that has such a setup. Their Moodle is plugged into a segment of the internal LAN/WAN which is designated as a DMZ zone (de-militarized zone). Any server/workstation connected to DMZ can be reached from both inside the private network and the outside public (internet) network. All traffic coming from any campus in that ISD shows to moodle as a single private IP address. Any traffic coming from the outside, however, does show the IP address of the workstation being used to access.
Have seen this, however, mis-configured networking/proxy ... a workstation of a private IP network discloses NOT the public IP gateway but the workstation 10. IP. Uhhhh, not good in that, it is possible to know which particular computer a user is using inside a private network. If I were really good at social engineering, I could possibly trick that user (via EMail or other means) into accessing/clicking upon something which installs a root kit or similar on their workstation. And to which I, as the 'bad guy', could connect or use.
Years ago I had a lot of fun with a fellow co-worker who was interested in Internet things, but simply couldn't understand why the need for security and restrictions. So, sent him an EMail with a thing called 'backorifice' as an attachment to the EMail disguised as 'coolmovie'. Knowing that he was 'into' online videos, no problem. He could NOT resist (of course, he also 'trusted' I wouldn't attempt anything malicious).
Anway, he clicked on the attachment ... it provided a nice little message saying something about an error, but the damage was done ... backorifice was installed. When he wrote back and said he couldn't open the attachment, that let me know I could now connect to his workstation via backorifice.
One of the things possible:
Multimedia control
Play wav files, capture screen shots, and capture video or still frames from any video input device (like a Quickcam).
So for a day or so, I would connect to his workstation and play an annoying wav file ... which made him think his computer was having serious hardware problems ... sounded like a harddrive whirling and grinding away ... even though his screen saver was on and he wasn't doing anything on computer at the moment and there was no scheduled process to be running at that time.
Lesson learned. ;)
Even if it were possible that Moodle could circumvent network settings, I for one, would NOT want Moodle to have that ability. It would mean one more thing for Moodle code to protect and what issues it would cause IF the Moodle server could be used as proxy for traffic headed outside to the internet. Users need to remember that if there is path one way, more than likely there is a return path. Boy what 'fun' students could have using Moodle as a proxy!
'spirit of sharing', Ken