Deep Guard - Internet Security
I having just discovered - after much mucking about - that Deep Guard has been the cause of a severe reduction in internet speed.
I recently had Fibre Optic Broadband installed and couldn't understand why the speed remained the same after it was installed (according to the online speed checker).
After activating and deactivating everything in Internet Security Suite I found the problem was with Deep Guard. With DG activated the speed read 2Mbps with DG deactivated the speed read 38Mbps.
You may already be aware of this, if so, sorry! If not I'm sure you will be able to rectify it at some point!