I have never seen this before but lately I have been receiving packet 0x4A when logging in. I receive it right after i receive 0x51. After packet logging, it seems that it containts a Null-terminated string "IX86ExtraWork.mpq".
Anyone have any idea what does is the purpose of this packet/what does the mpq do?

It get's information from your system if your using a real blizzard game.  If you checked that little box "send computer statistics to blizzard", that's how they get it.

o i c thanks

You may also get the packet unrecognized error on SphtBotv3:
Unrecognized BNCS packet SID_004A received:
0000:  49 58 38 36 45 78 74 72 61 57 6F 72 6B 2E 6D 70  IX86ExtraWork.mp
0010:  71 00                                            q.

On my old bot, I just put a notification: "It wants to to download <file>.  Ignoring it."

[quote author=iago link=topic=9868.msg92009#msg92009 date=1102824935]
On my old bot, I just put a notification: "It wants to to download <file>.  Ignoring it."
[/quote]
I do that, and check the FILETIME on the file, so the server will think I already have an up-to-date version.

That's probably the best idea is to just display that Battle.net sent you an optional request.  IIRC, if you do call it and return the results to Battle.net, they have to be sent before you log onto an account.  Battle.net sends you the optional ExtraWork request after a successful cdkey and version check.  Most bots that I've seen and/or used attempt to log onto their account after a successful cdkey and/or version check; so you would have to delay your logon and wait to see if Battle.net has sent you any such request before making your logon attempt.

Or you could just ignore it.

It gets sent to an error log if I ignore it.  It probably does on other bots too.  You should at least handle it somehow, even if you just handle it and do nothing.

That's what I meant by "ignore it." Create a handler that just does nothing.