There are always lots of discussions on the net on this subject but the answer is NO. A digital camera can process an image to correct lighting conditions which in the days of film you needed a filter. A PC can add special effects which again in the days of film you needed a filter.
Is it a good idea to attach a filter to your lens YES. Why? Well your lens hood (you must always use a lens hood) will provide some protection for the glass at the front of your lens from frontal impact but it will not always give 100% protection, nor can it protect from dust (which can be abrasive), finger marks, fluids splashed etc.
So what filter do you fit? Ideally one that has no impact on your images. UV and Skylight filters are easily found but both will have a slight impact on the image, even though your camera may re-compensate, there will be some digital noise (reducing the potential image quality). Filter manufacturers have recognised this and clear protection filters are now readily available. But lets just step back a moment, do you really need to be concerned? Well if you make a living from your images in a competitive field then yes, but then you probably do not use any filters and replace the lens if it is compromised. If like most of us your lens is occasionally used and will be kept for many years then any filter permanently attached is better than none as inevitably a replacement filter is easier and cheaper to replace.
So which filter should you buy? Big brands. Hoya, B+W, Sigma, Nikon, Canon are all respected but cost a bit. If your lenses are PRO quality and value, then do not skimp B+W MRC (Multicoated ) are what you should aspire to along with the top end of the Hoya range (visit their web site).
If you are an occasional photographer or a keen amature, then many of the £5-10 multicoated non branded filters on ebay are plenty good enough. Again it's protection you need and the camera or PC will process out any effects. In most cases you will not normally see a difference, but if you are that concerned then go ahead and spend the money.
If it is your image/street credentials that you are protecting, then the printing on the outer edge of most filters are hidden by the lens hood. If you want to fit in with the 'in crowd', then B+W proudly and quite rightly display their credentials on the visible section of the filter ring where everyone else can see it. Some of my filters are B+W I will let you muse as to why I bought mine.
If you read this and concur that the information is helpful then press the YES button. Thank you.