OB1

If they were using the Skype client I doubt it. Skype's communication is encrypted and not always directly between clients, there might be a server in the way. You could look for traffic to skype hosts, but they're not all known and now all obvious.

Google sites (sites.google.com) is only served over https, so you'll need a proxy capable of filtering https traffic.

Restricted youtube doesn't work on the app. The app does weird stuff™ and generally doesn't like having its traffic messed with. If you have MDM in place, you could install YouTube for Kids instead.

I'd advise you to look at this from the other side. Block Social Networking and allow the social networks you want to, it's likely to be a much shorter list.

Would you mind PM-ing me some examples? Historically web proxy detection has been one of our strong suits, so it's concerning to hear this.

Clear the cache / temp files and scan for spyware.

Have you tried the smoothwall.org forums? You're much more likely to get a helpful / knowledgeable response there. Most people on here have the commercial version of Smoothwall. community.smoothwall.org

Yup, sounds like Sisra doesn't understand auth. Find out which domains it's connecting to (we can't as we don't have the application) and make them authentication exceptions. Its not uncommon for applications not to understand proxies, so this is a bit of a get out of jail free card.

It's quite possible Sisra doesn't understand authenticating proxies. What's it not doing that it should? Also, in the realtime logs, where is it trying to connect to and what responses are you getting?

Allowing a domain allows the subdomains. It's the same with blocking. You might be getting blocked upstream. I'd be very careful about allowing deviantart outright. I think there's a NSFW filter on there but that can be bypassed by logging in. We'll have a look at it and see if we can come up with something.

Off the top of my head, iMessage doesn't actually use ports 80 / 443 exclusively, so if you're firewall's locked down that may have something to do with it. Snapchat doesn't like being decrypted and inspected either (most apps don't). Check your realtime web filter, if nothing's showing up in there then it's going to be firewall related.

Which search engine was it? And do you know if you are enforcing safesearch?

Do you have a record of what they searched for and which search engine they were using? PM me details if you have them. Otherwise, I'd follow @simoanorak's advice and add HTTPS decrypt and inspect too, although setting that up can be non-trivial depending on your environment. EDIT: Apparently, Dan types faster than me...

Our apologies if there has been any confusion. Your best option is to contact your account manager, I'm sure they'll be more than happy to clear things up.

The twitter app, like many, makes SNI-less connections to twitter over https. Most filters and proxies don't like this and with good reason. Your best bet is just to use the browser. Bear in mind, there is also a lot of questionable content on twitter generally.