Unidentified Downloads

I am running an iMac with OSX Yosomite.
I have internet connection using a 'Three' Mobile Wi-Fi dongle.
I have noticed an excessive Download taking place whilst I am not video streaming. I only use my machine for web site Browsing such as Newspapers and shopping sites and e-mails as such not a great deal of data is down loaded.
Back in December I noticed a high quantity of download on my ISP, one day 6gB was recorded another Day 1.5 gB in 60 minutes was recorded and this was whilst I was online but just monitoring the available download from the Three web site. Nothing else was running on my machine. I have always had disabled auto downloads of Apple Updated so I have no idea where this data was going.
I contacted Three and they said that download was being recorded through my dongle, but 6gB is a Shed Load load of Data. Three sent me a new Dongle and Sim Card and all seemed OK, but today I have noticed again 1.2 gB of download occurred in 60 minutes and later 0.6gB went in 15 minutes.
I tried to get Surplus Meter Software but my Security Software stops it downloading as it is not Apple Software.
So I am now at a loss as what to do. Excessive down load is being recorded but as far as I can see I am not downloading any data of the magnitude being recorded.
Please Can anyone give me any advice.

Have you wifi?
If so is it being shared openly, have you changed the passwords?
is your computer using internet connection sharing?

Windows updates are not usually that big

mattylad said:

Have you wifi?
If so is it being shared openly, have you changed the passwords?
is your computer using internet connection sharing?

Windows updates are not usually that big

Click to expand...

I thought I had covered all of those eventualities.
I have Wi-Fi and Mobile internet connection.
The Wi-Fi is not shared openly and is Password protected,
The passwords have not been changed, The Mobile Wi-Fi Dongle has recently been replaced by my ISP (Three) and the problem remains.
I am not running windows or Internet Explorer, I am using Apple OSX Yosomite with Apple Safari.
Windows update amy not be that big but the Upgrade from Apple Maverick to Apple Yosomite was in fact 5gB.
There is an awful lot of download involved here but I have no idea where it is going or what it is doing. I have AVC security running although that was recently installed to replace Kaspersky.
Regards

Maybe it backs your data up in the apple cloud. Download a network analyzer so you can see which program/service requires that much traffic!

mufcpavlos said:

Maybe it backs your data up in the apple cloud. Download a network analyzer so you can see which program/service requires that much traffic!

Click to expand...

The Network Analyser sounds like a good Idea - Have you any suggestions for a good one. I tried Surplus Meter but it doesn't seem to Work with Apple Yosomite.
I am not registered to iCloud for Data back up (I don't think).
It is a nightmare.
Yesterday there was 4gB of date registered to my account. I have used the Internet the same today and only 100MB of data registered.
Hope you can suggest a good Network Analyser.
Thanks for your help.

Ive never been a mac user so i cant suggest you any good programs. After a fast google search i came up with this result and it seems ok
http://www.iwaxx.com/debookee/

You need to spend sometime looking to the right direction and you will find it!

Thanks for the tip. I will have a look around right now.

Hysteresis said:

Thanks for the tip. I will have a look around right now.

Click to expand...

WOW!! mufc.
Ran that Debookee thing, but I can't understand a word or number of the reports. Pure Gobbledegook to a Numpty like me.

Try any or all of these and see if you can do your job easier
http://mac.appstorm.net/roundups/internet-roundup/4-ways-to-monitor-bandwidth-usage-on-your-mac/

'Little Snitch' will allow you to see all downloads activity and restrict any unwanted .