Some program settings will affect your connection.
Almost any program which uses the internet has settings that can affect it, including some security software, whose intent is to protect you online. This can vary from security firewalls being set to update or Microsoft Windows being set to download automatically, taking up some of your connection speed.
If you think a program may be affecting your broadband you'll find it's often difficult to pin down the culprit. A good rule of thumb is to try and disable the program and see if the broadband connection improves. If it does it's likely a setting in that program is affecting your connection.