In the proxy lists, there are many Level 0 proxies. The tutorial only mentions Levels 1 - 5, there's no mention of a Level 0 type proxy. Can someone please explain what Level 0 is?

Well I am going to have to claim a little bit of ignorance here my friend and perhaps some degree of neglegence. I generally do not go through the lists sumitted but am more focused on content of replys and posted comments. I have not noticed level 0 posted but , like you, am familiar with level 1-5. So, that being said, I defer to those who post those lists to explain or Insomniac - the proxy God. But I did want to add that, as I am sure you are aware, it is always prudent to retest any list that you plan to use. That being said... I wonder what they are testing as with you? Please understand that is not a contention but rather a question that I am curious about. I will certainly keep an eye out for them and retest myself.....

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If you don't fall deeply in love with this board in the first 10 seconds... you need to check your PULSE

There are a number of diferent Proxy grading systems, each one has diferent ways to grade whether or not a Proxy is infact Anonymous and how Anonymous it is. A Level 1 Proxy by definitions exhibits absolutely no leekage of variables, and also has the unique property that there is no RDNS records for its IP. This means that if a Proxy is lets say 203.129.16.4 and when you do a dns lookup on it, you will get no hostname. The primary diference between Level 1 and 2 is that Level 2 does indeed have a resolvable hostname. As far as Level 0 goes, I would personally view this as stating the Proxy is not Anonymous and therefore does not indeed have a Level, or atleast that level is undeterminable at the server side level, and instead of the level being defined as '?' it is defined as '0' as the variables do not spill the IP Address. If you check the specification of Proxy Judge 2.35 then you will see that the only levels it will display are "?,1,1?,2,2?,3,3?,4,4?,5,5?". So either the program you are using cannot decide on what Level the Proxy is, or it is its own way of stating the Proxy is not Anonymous. I would suggest a manual check of your results to see exactly how your program in question defines its Levels.