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bahb2
2005-11-04, 03:28
Since the latest version of Spybot, I'm unable to do all the updates unless I go to the web site, because one of the update portions responds with a "bad check sum" message. What does that mean?

Also, on my Windows XP Home computer, Spybot is checking 30746 items. But on my XP Pro computer, Spybot is only checking 15782. Is that as it should be?

Thanks much,
Bahb

spybotsandra
2005-11-04, 10:31
Hello,

Many users have reported that they are not able to download updates. The 'Search for updates' reveals updates, but they cannot be downloaded. Often a 'HTTP Error 403' or 'bad checksum' is displayed. This has a simple reason - millions of people trying to download from the same server, which can't handle such a burden. In combination with the growing size of the detection file this is becoming a serious problem. We are currently considering possibilities to improve the situation. This includes the search for additional servers and ways of more effective compression. At least one server will soon be added, others will follow hopefully.

In order to overcome the problem for now, if you try again, have a second look at the menu bar. It has a pull-down item to select a mirror. Click the arrow beside it, and select a different location (try the ones locatest nearest to you first), where you'll most probably have better chances to download.

This information is also available in our FAQ:
http://www.safer-networking.org/en/faq/20.html

For more informations on updating please do also have a look at this link on our website:
http://www.safer-networking.org/en/howto/update.html
In section 4 you'll see how to select a download location nearest to you.
If this sounds too difficult please try to download the updates manually:
http://www.safer-networking.org/en/download/index.html
Here is the direct download link:
http://www.spybotupdates.com/updates/files/spybotsd_includes.exe
Just download and run that file - it is self-installing.

For more information please have also a look into our forum:
http://forums.spybot.info/showthread.php?t=63&highlight=checksum

Further please run Spybot - Search & Destroy and switch to "Advanced mode" via the menu bar item "Mode" and select "Settings" --> "File Sets" in the left bar. There, please right-click somewhere into the list and "select all available checks".

Best regards
Sandra
Team Spybot

bahb2
2005-11-05, 01:35
Doesn't it seem strange that the server I used downloaded 2 of the 3 items I needed? I wouldn't call the server "busy", since I was already logged onto it and was successful with SOME items.

Is it out of the question that, instead of a message saying "Bad checksum", the message could be "server busy"? "bad checksum" sounds....well, bad. Like my machine's in jeopardy. of course now that I know that's equivalent to a busy signal, I can live with that. But it's reminiscent of the message that tells you the URL doesn't exist when what it actually means is your ISP just went off the air. Computers were built by geeks for geeks, I guess. Why else would the messages seldom mean what they say they mean?

Anyway, thanks for responding,
Bahb

bitman
2005-11-06, 07:32
Doesn't it seem strange that the server I used downloaded 2 of the 3 items I needed? I wouldn't call the server "busy", since I was already logged onto it and was successful with SOME items.
In the Internet world things can change in seconds. It's possible that the same server that was idling just a moment ago has hundreds more people attempting downloads a few seconds later. Each downloaded file requires a new 'connection' due to the HTTP download system used, there's not a 'login' to the download server itself. It's also even more likely that the file giving the Bad Checksum error was larger than the other two and so more likely to fail.

Is it out of the question that, instead of a message saying "Bad checksum", the message could be "server busy"? "bad checksum" sounds....well, bad. Like my machine's in jeopardy. of course now that I know that's equivalent to a busy signal, I can live with that. But it's reminiscent of the message that tells you the URL doesn't exist when what it actually means is your ISP just went off the air. Computers were built by geeks for geeks, I guess. Why else would the messages seldom mean what they say they mean?
I understand your issue, but let me help you understand the difficulty, As you've noticed and mentioned, "it's reminiscent of the message that tells you the URL doesn't exist when what it actually means is your ISP just went off the air". This shows great insight on your part, you just need to complete the thought. In reality it's impossible for your web browser to know if the URL doesn't exist, there's no such server, or your ISP, their ISP or some ISP in between is down. So the browser tells you the only thing it really 'knows', which is that it can't reach the URL so it 'doesn't exist'.

Now, let me explain that the 'Bad Checksum' message means that when the file download was completed and compared against a verification number for that file called a checksum, the computed value didn't match, thus resulting in a 'Bad Checksum' error which is....well, bad. Unfortunately, this same result can occur if the download itself actually fails since obviously the computed checksum for no or a partial file won't match that for the complete file.

Some situations where the download doesn't start properly are detected by the networking and result in different even more cryptic messages like "Socket Error #11004", which indicates the initial connection to the network has failed. Since these errors are generated deep within the TCP/IP networking itself, they're difficult to trap and modify for human understanding.

The situation where the networking on the PC is working and can reach the server, but fails anyway due to server overload, is a bit more difficult to detect. From the networking standpoint everything is working fine, so it doesn't create one of the cryptic messages like above. From Spybot S&D's (SS&D) standpoint, everything looks fine, but since the overloaded server only partially responds it eventually times out the attempt and simply returns to the next step, tries to verify the checksum and fails with Bad Checksum. Since SS&D has no information telling it that it only got part of the file or even no file at all, it has no way of knowing why the checksum doesn't match, it only knows there's a Bad Checksum, so it says so.

Now I will say here that it should be possible to detect some obvious conditions such as an empty (0 byte) file and even verify the length of the file received against a value included in the control file downloaded first to display the available updates. But the reality is that the end result would still be that the download failed and 'Bad Checksum' is a commonly understood term for such failures. It would be reasonable, however, to expect this term to be mentioned in the Updating, Help button information, which it isn't.

bahb2
2005-11-06, 08:29
Bitman, thanks ever so much for your patient teaching, answering other questions along the way, too. What a good teacher you are.

Blessings on you,
Bahb2