https over proxy safe from sniffing?

Question

Apparently all the google ads in my gmail(https) are being filtered. I'm worried. So it means somehow the data pass through the company proxy and being filtered?

Answer 1

The ads aren't necessarily loaded in the same http request as the rest of the gmail interface. It's possible they are loaded (in a separate frame) over http, rather than https. You should view the source and check.

Answer 2

Expanding on some of the other answers - assuming that your proxy isn't doing a MITM attack, all traffic through it will be encrypted, except for the very first CONNECT method, which is transmitted in the clear. This method tells the proxy the hostname and port to establish the SSL connection to. Everything after that is encrypted. So, it is possible for the proxy to block connections to "ads.google.com" for example.

Answer 3

1. The filter may be software on your computer (assuming this is a company computer.)
2. As indicated by emgee, the ads may not be over SSL.
3. Some companies set up their machines with an SSL key to allow SSL connections to go through their proxies. You can check this by reading the whole chain of the SSL cert. (This is what is being alluded to as a man-in-the-middle attack by other answers, though that's stretching the definition a little.)
4. You may also be connected to a DNS server (company's or otherwise) that is blocking resolution of the domain the ads are being served from.

Also, keep in mind that most companies have policies allowing them to view all of your activity on a company machine. Most companies also have the ABILITY to do so, it's pretty trivial. And even if the company doesn't have a policy explicitly stating this, most states give companies the implicit right: they did pay for the machine and are paying for your time, so what you do is considered theirs to monitor.