A spot filter is one rule (a one line spot filter) or multiple rules (multiple line spot filters) that a user can setup within DXSpider to control which specific spot(s) are received at the shack console. These configurable filters/rules reside on the DXSpider node and are stored along with the user's other information. Filters can be likened to a car wash . . . . . like cars, information goes in one end dirty, gets washed and comes out the other end cleaned.
All spots received from other users on the cluster, or those received from other nodes, start out life destined for each and every connected user's console. If spot filtering has been configured, all spots headed for that user first go into the filter input, are processed and sent out the other end of these filters before being sent to the user's console. Like a car wash, each spot goes through one or many stages depending on whether the user wanted a simple or a super-duper filtering job. Along the way, the spot gets scrubbed, unwanted information removed or wanted information passed on and finally the wanted spots only are spit out the other end - nice and clean with all unwanted "stuff" sent down the drain to the infamous "bit-bucket."
For example, let's say our local user has never owned a microphone in his life and definitely doesn't want to see any of those useless SSB spots. Our user simply sets up a basic filter to reject any SSB spots before they reach the user's console. Similarly, it's now the ARRL CW DX contest weekend, so not only does our user not want to see SSB spots, but now doesn't want to see any UHF, VHF, DATA or any US/Canadian "DX" spots. Our user now only accepts HF CW CONTEST spots and in the same rule rejects spots for W and VE stations. In these and many more situations, "filters are our friends."