Opponent Used Disconnect Program

Sorry, but the only way that's possible is if they hacked Chess.com and either:

• Tricking the server into thinking that you've disconnected
• Spamming your laptop/wi-fi router with so many requests (they need to find your IP, which they can only get from Chess.com if they don't have physical access to your laptop) that the wi-fi malfunctions.

Have any actual developers looked at this? Speaking on something out of your depth saying it's impossible because you don't see how it's possible actually does more harm than good.

I write Javascript for a living and specifically  use Websockets in production (I did a quick view-source and it looks like Chess.com is using Angular and probably a socket wrapper like Socket.io), so I see more possibilities here. If the server isn't smart enough about filtering user input then one client could send excessive requests to the other (a sort of peer-to-peer DoS), or, it could send malformed responses and cause an exception in the client-side code, causing a disconnection. Back in the days of AOL Instant Messenger there were programs called "punters" that did exactly this. Each generation makes the same mistakes as the last

For example, if a socket is shipping JSON-encoded responses back and forth, then improper parsing of input can inject invalid character sequences into the stream which cause JSON.parse() to fail (as the JSON standard demands that certain special characters called control characters be escaped in a \uXXXX format). That's merely one example (from a real bug in a real application). There's all sorts of possibilities, so don't write it off so quickly.

Thanks Williamfwm. It's actually impossible since the server decides what to send to the other user, not the client. Client -> server -> client. Filtered. Protected. There is nothing possible that the other player can send that would overwhelm the other user. Only moves, chat, and friend requests are sent. Those are rate limited or one-off messages. There is no way to interfere with another user's client. 

This logic to "prove" the existence of disconnecting programs (you can't prove it doesn't exist, therefore it exists) is faulty - you might as well say that there is a teacup with a face of an elephant on it floating in the asteroid belt, since you can't prove that it doesn't exist.

The tea cup is there man, I seen it with my telescope!

How do I block these cheaters?

If you read the thread, you will understand that what you are complaining about is not possible.

TLDR

When ever I was close to win a game I got disconnected... it is very much annoying ...I do not if the Chess.com is looking in to this seriously.

LouStule, I had the exact same thing last night - way ahead and DISCONNECTED came up ...

But it was probably my wifi!

I quit playing Blitz on your site due to that problem I don't know whose fault it is but I do know that I've never had a disconnect where I won. I have only been playing chess for 2 years so for now I'm just playing daily correspondence this gives me longer to analyze the positions and hopefully I won't keep making the same mistakes over and over again like I was when playing Blitz.

It's literally impossible. If you don't want to listen to facts, there's not much we can do for you.

That's called confirmation bias. There is no problem.

I was playing a few games very smoothly and was winning. Than at one game, I was left with 10 sec on 3 min game. And i make the move that checkmate my opponent. Once i make the move. The game hung. And while i was waiting for the checkmate sign. No sign show up. Suddenly, a disconnection sign show up. I refresh the page and when i try to make the move at less than 5 sec, on the 3rd sec it expired before my queen reach to its destination and i lost. Need to really stop the clock if disconnection happen. Or else, some players will use this.

What the OP describes is impossible without first compromising chess.com.  The only things that go back and forth over the wires between me and this site are moves and text.  I've never seen anyone cheat; of course, I play mostly five minute blitz where that's hard to do.  The only noteworthy thing I've seen so far:  I was playing a South Korean, and suddenly, for about a dozen moves, his responses were absolutely instantaneous after I had executed my moves, but...HE STILL LOST!  That isn't cheating, just fast game action, and those people are very much into gaming and have got fast action down.  I cackled at him from my seat in Oregon "You so smaht." 

Pre-moving.

I've heard about pre-moving but don't quite understand how it works.  I can understand how a pre-loaded standard opening would work, but this sequence STARTED over a dozen moves into the game, in a complex position nobody could possibly have been able to predict in advance, so wouldn't he have been better off just looking at the board as it existed at time t and waiting to see what I would do?  It was like facing the fastest gun in the West (or in his case, the East), but he couldn't quite hit what he was shooting at.